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Antioxidant, anti-inflammatory and wound healing properties
of medicinal plant extracts used to treat wounds and dermatological
disorders
S. Ghuman
a
, B. Ncube
a,d
,J.F. Finnie
a
,L.J. McGaw
a,b
, E. Mfotie Njoya
b
,R.M. Coopoosamy
c
, J. Van Staden
a,
⁎
a
Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa
b
Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
c
Mangosuthu Universityof Technology, Department of Nature Conservation, P O Box 112363, Jacobs 4026, South Africa
d
Agricultural Research Council (ARC), Vegetable and Ornamental Plants (VOP), Private Bag X923, Pretoria 0001, South Africa
abstractarticle info
Article history:
Received 23 April 2019
Received in revised form 1 July 2019
Accepted 5 July 2019
Available online xxxx
Edited by JJ Nair
Medicinalplants used for woundhealing and skin diseases are key to unlocking the doorsto combating resistance
of pathogens to pharmaceuticals andallopathic management. This study was aimed atscreening the antioxidant
effects, the anti-inflammatory activity and wound healing capacity of traditional medicinal plants used in the
treatment of skin conditions and wound healing in KwaZulu-Natal, South Africa. Eleven plant species were se-
lected and separated into different plant parts (bulbs, roots and leaves) and extracted using 50% aqueous meth-
anol. The extracts were assessed for their anti-inflammatory activity using the nitric oxide release and
lipoxygenase inhibition assays. Almost all plant species exhibited some degree of anti-inflammatory activity.
The observed antioxidant results (DPPH, FRAP, CLAMS) were significant for many of the extracts. The LOX re-
vealed that five of the medicinal plant extracts, Bulbine natalensis,Eucomis autumnalis,Hypericum aethiopicum,
Tetradenia riparia and Zantedeschia aethiopica were effective as anti-inflammatory agents with IC
50
values
below the quercetin control andranged from 3.55 ± 0.11 to 9.52 ± 0.11 μg/mL. The results of the wound healing
assay/protein precipitating activity weresignificantly excellent for the three Aloespecies, two Bulbinespecies and
support scientific evidence from previous research. The protein-precipitating capacity as a wound healing model
was significant for Haworthia limifolia 82.71 ± 0.74% while the rest of the plant extracts had moderate to low
values. In addition, medicinal plant extracts from E. autumnalis,H. limifolia,H. aethiopicum,T. riparia,andZ.
aethiopica demonstrated promising and beneficial results for potential use in the treatment of skin diseases
and wound healing. Antioxidant assays as well as anti-inflammatory assays (nitric oxide release and
lipoxygenase inhibition assays) and wound healing assays support the dermatological and wound healing
usage of these traditional medicinal plants and warrants further investigations and possible isolation of bioactive
principles. Overall, the results from this multi-dimensional medicinal plant study provide extensive information
on the 11 plant species and their various plant parts.
© 2019 SAAB. Published by Elsevier B.V. All rights reserved.
Keywords:
Anti-inflammatory
Antioxidant
Dermatological
Medicinal plants
Wound healing
1. Introduction
The mammalian immune system is comprised of many interactive,
specific types of cells that co-operatively safeguard the human body
from pathogenic infections and other sources of stimuli. Chronic inflam-
mation is pivotal to skin pathologies and delayed healing of wounds in
diseases like leprosy and sexually transmitted infections (Allen, 2003).
According to Iwalewa et al. (2007), plants contain an array of natural
compounds which have effects onthe healing process and the potential
to inhibit or reduce the inflammatory process. A study conducted by
Johnson (2009) emphasised the importance of research in addressing
the lack of alternative drugs, the promotion and development of new
drugs as well as the management of therapeutic processes like inflam-
mation and related metabolic conditions. The process of inflammation
is a huge burden to human health care and involves many diseases
(Edwards, 2005). Although there are multiple drugs available, many of
the drugs that are anti-inflammatory agents come with extensive
side-effects and have limited clinical use (Viola et al., 2008). The
South African Journal ofBotany xxx(2019) xxx
Abbreviations: ANT, Antioxidant activity; BSA, Bovine serum albumin; CLAMS, β-
Carotene linoleic acid model syst em; COX, Cyclooxygenase; DPPH, 2,2-Diphenyl-1-
picryhydrazyl; FRAP, Ferric-reducing antioxidan t power; LOX, Lipoxygenase; MEM,
Minimal Essential Medium; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo-lium
bromide; NO, Nitr ic oxide; ORR, Oxidation rate ratio; SDS, Sodium dodecyl sulphate;
UKZN, University of KwaZulu-Natal.
⁎Corresponding author at:Research Centre for PlantGrowth and Development, School
of Life Sciences , University of Kwa Zulu-Natal, Pie termaritzburg, Private Bag X01,
Scottsville 3209, South Africa.
E-mail address: rcpdg@ukzn.ac.za (J. Van Staden).
SAJB-02463; No of Pages 9
https://doi.org/10.1016/j.sajb.2019.07.013
0254-6299/© 2019 SAAB. Published by Elsevier B.V. All rights reserved.
Contents lists available at ScienceDirect
South African Journal of Botany
journal homepage: www.elsevier.com/locate/sajb
Please cite this article as: S. Ghuman,B. Ncube, J.F. Finnie, et al., Antioxidant, anti-inflammatory and wound healing properties of medicinal plant
extracts used to trea..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.07.013
demand for safe and effective drugs that have anti-inflammatory prop-
erties are essential for the future of dermatological and wound healing
care.
Inflammation can be defined as a localised protective, non-specific
immune response of vascular tissues to harmful stimuli such as dam-
aged cells or irritants and pathogens (Ferrero-Miliani et al., 2007). It in-
volves a series of initialresponses from the immune system to infection
transferring immune cells to the site of injury. In addition, inflammatory
reactions serve to establish a physiological barrier against the spread of
infection and to promote healing of any damaged tissue following the
clearance of the stimuli (Cohn and Langman, 1996). A defence mecha-
nism of inflammation is evoked by body tissues in response to chemical
perturbation and microbial infection that results in cell injury or death
(O'Byrne et al., 2000; O'Byrne and Dalgleish, 2001). The inflammation
mechanisms involve various events involving themetabolism of arachi-
donic acid which plays a critical role. The defensive response is
characterised on the skin as redness, pain, heat and swelling resulting
in a loss of function in the injured area. When tissue cells become in-
jured they release kinins, prostaglandins and histamine (O'Byrne et al.,
2000; O'Byrne and Dalgleish, 2001). Collectively, these compounds in-
crease vasodilation and permeability of the capillaries leading to in-
creased blood flow to the injured site. Short-term inflammation is the
early reaction of the body to detrimental stimuli and is an outcome of
the amplified movement of plasma and leukocytes especially
granulocytes from the blood into injured tissues (O'Byrne et al., 2000;
O'Byrne and Dalgleish, 2001). Numerous biochemical events unfold, in-
creasing the inflammatory response. These include the immune system,
various cells within the injured tissues and the local vascular system.
Long term inflammation occurs with an advanced shift in the type of
cells present in the site of inflammation characterised by simultaneous
destruction and healing of the tissue from the inflammatory process
(Tortora et al., 2016). Prostaglandins and leukotrienes are produced
from arachidonic acidand are responsible for the complex process of in-
flammation and pain. Jäger et al. (1996),Foegh et al. (1998) and Graf
et al. (2005) reported that flavonoids such as quercetin inhibit
lipoxygenase enzymes which impact on pro-inflammatory prostaglan-
dins and leukotrienes. These are metabolised by the LOX pathway to
hydroperoxy-eicosatetraenoic acids and leukotrienes that are impera-
tive biologically active mediators in a variety of inflammatory processes
(Piper et al., 1994; Alitonou et al., 2006). Stimuli of neutrophils causes
the cleavage of arachidonic acid from the membrane phospholipids
which are then transformed into leukotrienes and prostaglandins
through LOX pathways (Bouriche et al., 2005). Prostaglandins have nu-
merous effects on physiologicalprocesses such as muscle relaxation, va-
sodilation, aggregation of blood platelets, cell protection, pain and fever
control (Graf et al., 2005; Bedini et al., 2009). The processes of inflam-
mation include processes with reactive oxygenation that are initiated
by the stimulation of leucocytes.
Myrtle and eucalyptus essential oils caused temporary leucocyte ac-
tivation by scavenging hydroxyl radicals and consequently interfering
with the process of inflammation by acting as antioxidants
(Grabmann, 2000). Antioxidant properties also provide some insights
into the possible activity of a drug on inflammatory processes (Njenga
and Viljoen, 2006). A combination of studies on LOX, nitric oxide (NO)
and antioxidant evaluation is a good sign of the potential ant-inflamma-
tory activity of medicinal plant extracts (Alitonou et al., 2006). Nitric
oxide is one of the many oxides of nitrogen, a colourless gas, a free rad-
ical with anunpaired electron on the nitrogen atom. Nitric oxide is a sig-
nalling molecule with an important function in inflammation
pathogenesis and provides an anti-inflammatory effect in normal phys-
iological conditions. Nitric oxide is an inflammatory mediator that in-
duces inflammation as it is overproduced in irregular physiological
circumstances (Sharma et al., 2007). Researchers have reported that
NO is a powerful neurotransmitter effective at the neuron synapses,
contributing to apoptosis regulation and is involved in inflammatory
pathogenesis of disorders in joints, the gastrointestinal and respiratory
systems (Sharma et al., 2007; Rao et al., 2010). Nitric oxide inhibitors
are effective in the management of inflammatory diseases. Arginine an-
alogues and discerning biosynthesis inhibitors of NO are known to re-
duce inflammation. Excessive production could lead to tissue damage,
vasoconstriction and stimulation of mediators for inflammatory activity
(Sharma et al., 2007; Rao et al., 2010).
Polyphenols are carbon-based aromatic phenyl ring compounds
which oxidise to quinones by reactive oxygen species, a characteristic
responsible for the antioxidant activity and anti-inflammatory activity
(Sreejayan and Rao, 1996) in most plant extracts. The structural and
functional diversity of phytochemicals are the underlying pharmaceuti-
cal capacity for antioxidants, wound healing and inflammatory proper-
ties in medicinal plants. A wide variety of agents have been reported as
5-LOX inhibitors with the majority appearing to be reducing agents that
are lipophilic including partially saturated aromatics, phenols and com-
pounds with heteroatom–heteroatom bonds. Many are not selective 5-
LOX inhibitors, but often affect COX and other LOXs as well. In vivo sys-
temic activity for many of these hasin general been disappointing, prob-
ably because of poor bioavailability caused by lipophilicity and
metabolic instability (oxidation, and conjugation of phenolic com-
pounds). However, topically a number of agents have shown promise
for skin inflammation, with Syntex's lonapalene being the most ad-
vanced of these (Bishayee and Khuda-Bukhsh, 2013). In an effort to ex-
pand on the wound healing management agents, this study sought to
evaluatethe antioxidant, anti-inflammatory and wound healing proper-
ties of some selected medicinal plants used in the management of
wounds and related conditions.
2. Materials and methods
2.1. Plant identification, selection and collection
The identification, selection and collection of medicinal plants was
based on their reported traditional uses and demand in treating wounds
in KwaZulu-Natal province. The collection of fresh samples allowed for
immediate processing of fresh plant material parts prior to extraction.
All 11 of the plant species were available at, and collected from, the
Silverglen Plant Conservancy,situated in Chatsworth, Durban, South Af-
rica. Voucher specimens were prepared and verified by an experienced
horticulturalist at the conservancy and deposited at the John Bews Her-
barium, University of KwaZulu-Natal (UKZN) in Pietermaritzburg. The
plant materials were dried in an oven at 50 °C and thereafter pulverised
into fine powders and stored at room temperature in airtight glass bot-
tles. The plant species used in the study are as represented in Table 1.
2.2. Plant material preparation
For this study aqueous methanol (50% v/v) was used to extract pow-
dered ground samples of plant sample. This process was carried out
using a sonication bath with ice for an hour together with 20 mL/g
(w/v) of extractant. The crude plant extracts were concentrated by vac-
uum and filtered in a Büchner funnel through Whatman No. 1 filter
paper and concentrated in vacuo at 35 °C using a rotary evaporator
(Rotavapor-R, Büchi, Switzerland). All of the concentrated extracts
were then dried at room temperature using a fan and then stored at 4
°C until they were used for various assays.
2.3. Cell culture preparation
The RAW 264.7 macrophage cell lines were purchased from the
American Type Culture Collection (ATCC) (Rockville, MD, USA) and cul-
tured in plastic culture flasks in DMEM containing L-glutamine supple-
mented with 10% foetal calf serum (FCS) and 1% PSF (penicillin/
streptomycin/fungizone) solution under 5% CO
2
at 37 °C. The solution
was split bi-weekly and all cells were distributed in 96-well microtitre
plates.
2S. Ghuman et al. / South African Journal of Botany xxx (2019) xxx
Please cite this article as: S. Ghuman,B. Ncube, J.F. Finnie, et al., Antioxidant, anti-inflammatory and wound healing properties of medicinal plant
extracts used to trea..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.07.013
2.3.1. Quantification of NO release
The concentration of NO in the culture medium was evaluated using
the Griess reagent assay (Hunter et al., 2013). A 96-well plate was used
to culture the RAW 264.7 cells at 10
5
cells/well. Seeding the wells at 10
5
or 100,000 cells per well was done by quantifying the number of cells in
the cell culture medium first. An aliquot of cells was counted using a
haemocytometer which enables the calculation of the number of cells/
mL. The cell suspension was then diluted to the required concentration
using fresh medium before pipetting the known number of cells intothe
wells. The cells were washed with a buffer solution, Phosphate Buffered
Saline (PBS), frequently used in research of a biological nature, a water-
based salt solution containing disodium hydrogen phosphate 1.42 g/l,
sodium chloride 8 g/l, potassium chloride 0.2 g/l and potassium
dihydrogen phosphate 0.24 g/l. The osmolality and ion concentrations
of the solutions match those of the human body (isotonic). The pH
was adjusted to 7.4 with HCl and distilled water added to form a total
volume of 1 l. The resultant 1x PBS had a final concentration of 10 mM
PO
4
3−
, 137 mM NaCl, and 2.7 mM KCl. The cells were then pre-treated
with several concentrations of plant extracts and 1 μg/mL of LPS for
24 h. When pre-treating the cells, defined concentrations of plant ex-
tract (100, 50, 25 and 12, 5 μg/mL) together with LPS stimulates NO pro-
duction in the medium in which the cells are incubated. The
supernatant (100 μl) was combined with the equivalent volume of
Griess reagent and placed into an incubator for 15 min in the dark.
The absorbance of the water-soluble purplish-red product was read on
a BioTek Synergy microplate reader after10 min at 550 nm. The amount
of NO was calculated by a calibration curve established with 0.15–100
μMNaNO
2
. The inhibition percentage was calculated based on the abil-
ity of the extracts to inhibit NO formation by cells compared with the
control (cells in media without extracts containing triggering agents
and DMSO), which was considered as 0% inhibition. A graph of percent-
age inhibition against the concentration of the different compounds
were used to calculate the IC
50
values.
2.3.2. Cytotoxicity of LPS-activated RAW 264.7 macrophages
The cytotoxicity assay, MTT colorimetric assay 3-(4,5-dimethy-
lthiazol-2-yl)-2,5-diphenyltetrazo-lium bromide) used in the study is
as described by Mosmann (1983) and McGaw et al. (2000),withslight
modifications. The plant extracts were tested for cytotoxicity against Af-
rican green monkey Vero kidney cells obtained from the Department of
Veterinary Tropical Diseases (University of Pretoria). The cells were
maintained in Minimal Essential Medium (MEM, Whitehead Scientific)
supplemented with 0.1% gentamicin (Virbac) and 5% foetal calf serum
(Highveld Biological). Cell suspensions were prepared from confluent
monolayer cultures and plated at a density of 5 × 10
4
cells into each
well of a sterile 96-well microtitre plate. The plates were incubated for
24hat37°Cina5%CO
2
incubator until the cells were in an exponential
phase of growth and the subconfluent cells in the microtitre plate were
used in the cytotoxicity assay. Stock solutions of the plant extracts (200
μl) were serially diluted in MEM and added to the cells. The viable cell
growth after 120 h incubation with plant extracts was determined
using the tetrazolium-based colorimetric assay (3-(4,5-dimethyl-
thiazol)-2,5-diphenyltetrazolium bromide (MTT)), (Sigma) described
by Mosmann (1983). Untreated cells and a positive control (Doxorubi-
cin chloride, Pfizer Laboratories) were included. The amount of MTT re-
duction was measured immediately by detecting absorbance using a
Chromate 4300 microplate reader at 540 nm and a reference wave-
length of 630 nm. The wells in column 1, containing medium and MTT
but no cells, were used to standardise the plate reader. The LC
50
values
were calculated as the concentration of test compound resulting in a
50% reduction of absorbance as compared to untreated cells. The inten-
sity of colour was directly proportional to the number of surviving cells
and viable cell growth. Tests were carried out in quadruplicate and each
experiment was conducted in triplicate.
2.3.3. Lipoxygenase (LOX) inhibition assay
This evaluation was conducted using the guidelines of a procedure
described by Pinto et al. (2007) with minor modifications. The assess-
ments were based on measuring the production of the composite
Fe
3+
/xylenol orange usinga spectrophotometer at 560 nm. The enzyme
15-lipoxygenase from Glycine max was incubated with plant extracts or
a standard inhibitor at 25 °C for 5 min. Then linoleic acid (final concen-
tration 140 μM) in Tris–HCl buffer (50 mM. pH 7.4) was added and the
mixture was incubated at 25 °C for 20 min in the dark. The reaction
was terminated by the addition of 100 μL of FOX reagent consisting of
sulphuric acid (30 mM), xylenol orange (100 μM), iron (II) sulphate
(100 μM) in methanol/water (9:1; v/v). For the control, only LOX solu-
tion and buffer were pipetted into the wells. The enzyme LOX waspres-
ent in the blanks during incubation and the substrate (linoleic acid) was
added after theFOX reagent. The inhibitory activityof lipoxygenase was
determined by calculating the inhibition percentage of hydrogen perox-
ide produced from the modifications in absorbance values at 560 nm
after 30 min at 25 °C. Inhibition percentage was calculated as follows:
Percentage inhibition
¼Acontrol–Ablank
ðÞ–Asample–Ablank
=Acontrol–Ablank
ðÞ
100
where, A
control
is the absorbance of control well, A
blank
is the absorbance
of blank well and A
sample
is the absorbance of sample well.
2.4. Antioxidant activity of plant extracts
2.4.1. 2, 2-Diphenyl-1-Picryhydrazyl (DPPH) radical scavenging activity
The DPPH free radical scavenging activity of the 19 plant extracts
were determined using the assay as described by Karioti et al. (2004).
Dried methanolic plant extracts were re-dissolved to 10 mg/mL in 50%
(v/v) aqueous methanol. Various concentrations (1, 0.5, 0.25, 0.125,
0.0625, 0.031, 0.015, 0.0008 mg/mL) of the diluent plant extracts were
tested. Ascorbic acid and butylated hydroxytolulene (5, 10, 20, 40, and
80 mg/mL), were used as positive controls while the reaction mixture
with 50% methanol instead of the extract was used asa negative control.
Each sample extract was evaluated in triplicate.
2.4.2. Ferric-reducing antioxidant power (FRAP) assay
The ferric-reducing power of the plant extracts were evaluated ac-
cording to Ndhlala et al. (2013) and Moyo et al. (2010) with slight mod-
ifications from Kim et al. (2009).
Table 1
IC
50
(μg/mL)of nitric oxide of different medicinalplant extracts usedfor skin dis-
orders and wound healing.
Plant extracts IC
50
(μg/mL)
Aloe arborescens leaf N100
Aloe aristata leaf N100
Aloe ferox leaf N100
Bulbine frutescens leaf
a
26.32 ± 0.69
Bulbine frutescens root 42.51 ± 1.69
Bulbine natalensis leaf 54.79 ± 13.47
Bulbine natalensis root
a
28.64 ± 4.58
Eucomis autumnalis leaf 38.09 ± 2.21
Eucomis autumnalis bulb/root 63.10 ± 6.59
Haworthia limifolia leaf N100
Hypericum aethiopicum leaf
a
22.47 ± 3.87
Merwilla plumbea leaf
a
29.35 ± 0.55
Merwilla plumbea bulb
a
22.04 ± 0.20
Merwilla plumbea root
a
26.93 ± 2.60
Tetradenia riparia leaf
a
13.99 ± 2.47
Tetradenia riparia stem
a
2.05 ± 1.18
Zantedeschia aethiopica leaf 57.94 ± 2.22
Zantedeschia aethiopica stem 46.22 ± 5.52
Quercetin 6.30 ± 0.41
a
Bold indicates the plant extracts with excellent active anti-inflammatory
activity.
3S. Ghuman et al. / South African Journal of Botany xxx (2019) xxx
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2.4.3. β-Carotene linoleic acid model system (CLAMS) assay
The method used by Miller (1971),Miller et al. (1993) and mod-
ified by Amarowicz et al. (2004) and Ndhlala et al. (2014). The anti-
oxidant activity (ANT) of the samples were expressed as percentage
of inhibition of the rate of β-carotene bleaching: Antioxidant activity
was further expressed as the oxidation rate ratio (ORR). Quercetin,
BHT (6.25 mg/mL) and ascorbic acid were selected as positive con-
trols. The negative control used was 50% aqueous methanol in
place of the sample. Antioxidant activity was further expressed as
the oxidation rate ratio (ORR).
2.5. Wound healing properties of plant extracts
2.5.1. Protein precipitable phenolics capacity assay as a wound healing
model
The protein-precipitating capacity of the phenolics assay as outlined
by Makkar (1999) was used. Of the 19 plant extracts, 13 were selected
(Table 4) and tested for their wound healing ability from a comparison
of all the results of previous assays.
2.5.1.1. The formation of the phenolic–protein complex. Re-dissolved 50%
aqueous methanol extracts were added to 2 mL of bovine serum albu-
min (BSA) solution (with 1 mg BSA/mL acetate buffer), to produce a 3
mL solution (in increasing concentration of 50% aqueous methanol ex-
tract vs 50% aqueous methanol as follows: 0.95, 0.90, 0.85, 0.80, 0.75,
0.70 mL of 50% methanol with various concentrations (0.05, 0.10, 0.15,
0.20, 0.25, 0.30 mL) of the plant extracts. This was done in triplicate in
centrifuge tubes. A vortex was used to mix the solution and it was
then allowed to stand overnight at 4 °C in a centrifuge tube in the refrig-
erator. The tubes were centrifuged at 1370×gfor 10 min. The superna-
tant was carefully removed while the precipitate remained at the base
of the tube. The precipitate was then constituted with 1.5 mL of 1% so-
dium dodecyl sulphate (SDS) solution and vortexed until fully dis-
solved. The dissolved phenolic-protein complex was measured and
determined at 510 nm.
2.5.1.2. Determination of phenolics in the phenolic–protein complex.
One mL aliquots of soluble phenolic–protein complex dissolved was
placed into clean test tubes. A 3 mL solution of SDS-triethanolamine
(1% SDS (w/v) and 7% (v/v) triethanolamine in distilled water) was
added followed by 1 mL ferric chloride reagent (0.01 M FeCl
3
in 0.1
M HCl). The measurements were recorded using absorbance readings
at 510 nm after 30 min of incubation at room temperature using a
UV–Visible spectrophotometer. These readings were taken in tripli-
cate and the average converted into gallic acid equivalents using a
standard curve. A linear regression curve was plotted using GraphPad
Prism V6 (Graph Pad
R
software Inc. CA). The graph plotted phenolics
precipitated as gallic acid equivalents and mg dry plant extracts. The
slope (mg phenolics precipitated/mg plant samples = x) represented
the protein-precipitating phenolics in the medicinal plant extracts
(Makkar, 1999).
2.5.1.3. The protein-precipitating capacity as a percentage of total
phenolics. Aliquots of 0.05–0.30 mg/mL of the 50% aqueous methanol
extracts prepared to 1 mL with 1% of SDS and 3 mL of the SDS-
triethanolamine solution to which 1 mL ferric chloride reagent was
added. Incubation of the solution at room temperature for 30 min was
allowed followed by the measurement of absorbance readings at 510
nm. The graph constructed was a linear regression curve with phenolic
acid equivalents and mg extract prepared using GraphPad Prism soft-
ware. The slope of the curve (mg phenolics equivalent/mg extract =
y) represented total phenolics. The protein-binding precipitating
phenolics were measured as x.
The percentage %ðÞof total phenolics which can precipitate protein
¼x=yðÞ100
3. Results and discussion
3.1. Inhibition of NO activity
Values of the IC
50
for the flavonoid control, querc etin was 6.30 μg/mL
(Table 1).All plant extract values were considered in relation to thecon-
trol. Values greater than 100 μg/mL indicated less active anti-inflamma-
tory agents and plant extracts that fell in this category from this study
were the leaf extractsof the three Aloe species (A. arborescens ,A.aristata,
and A. ferox)andH. limifolia (Table 1). There seems to be a marked dif-
ference between the leaf and the stem extracts of T. riparia in terms of
the inhibition potential of NO with the stem demonstratingan excellent
and almost seven-fold efficacy to that of the leaf extract with an IC
50
value of 2.05 μg/mL. This marked difference between the two plant
parts may suggest that the levels or type of compounds produced by
the two may be different hence the differences in the observed activity.
It is also worth notingthat the IC
50
for the stem extract was higher than
that of the positive control, highlighting its potential as an anti-inflam-
matory agent. Significantly good IC
50
values were also observed for H.
aethiopicum leaf extract (22.47 μg/mL) and M. plumbea extract for the
leaf at 29.35 μg/mL, the bulb at 22.04 μg/mL and the root extract at
26.93 μg/mL. In addition, B. natalensis root extract had an IC
50
of 28.64
μg/mL and B. frutescens leaf extract at 26.32 μg/mL were both signifi-
cantly active anti-inflammatory characteristics towards NO inhibition.
The inflammation process is a highly complex pathophysiological
process which occurs when various processes of a variety of molecules
and mediators that are signalling, occur in a series of catalytic enzymatic
reactions (White, 1999). Many plant extracts are known to exert their
inhibitory enzyme effects via a range of diverse action mechanisms
and target sites (Capone et al., 2007). Many studies with various plant
species have also shown good NO inhibitory activity (Jäger et al.,
1996; Taylor and Van Staden, 2001; Jäger and Van Staden, 2005;
Fawole et al., 2009). The results of this study show that the enzyme in-
hibitory activity of stem, bulb, leaf and root extracts of the different
plant parts were significant in their anti-inflammatory capacity. What
does this mean for medicinal use in skin disorders and wound healing?
Dzoyem and Eloff (2015) reported that cytotoxicity and inflammation
occur when over-production of NO occurs in the body. NO production
is important as an inflammatory agent. Quercetin as a positive control,
significantly reduces NO production in the LPS-stimulated RAW 264.7
murine macrophage cell lines (Dzoyem and Eloff, 2015) and plant ex-
tracts that exhibit such characteristics have potential to serve as anti-in-
flammation agents.
Fig. 1 shows the outcomes of the MTT assay used to determine the
percentage of cell viability for the different plant extracts. NO inhibition
of the plant extracts was associated with their cytotoxicity on RAW
264.7 macrophages. The results of cell viability levels were high for
most of the extracts at lower concentrations. The capacity for medicinal
plants to be used in themanagement and the healing process of wounds
and skin diseases may be supported by this assay. Its importance as a
tool in identifying the effects of the various plant extract concentrations
on the viability and/or survival of mammalian cells was observed. The
plant extract activity which is inhibitory on NO production by induced
RAW 264.7 macrophage cell lines indicated good activity for low cyto-
toxicity and low production of NO for plants used in wound healing
and skin conditions (Adebayo et al., 2013, 2015). The release of NO pro-
motes inflammation, and thus the extracts act as foragers of NO and NO
production inhibitors, together with low cytotoxicity which isindicative
of mitigating the proliferation of inflammation by NO. The NO
4S. Ghuman et al. / South African Journal of Botany xxx (2019) xxx
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production inhibition in medicinal plants may be due to inducible nitric
oxide synthase activity expression (Lee et al., 2003, 2007, 2010).
3.2. LOX inhibitory activity
One of the important objectives of this study was to determine the
activity of the selected extracts for anti-inflammatory capacity using a
LOX model of inhibition. Table 2 provides details of the IC
50
(μg/mL)
values using the quercetin control inhibition of 15.91 μg/mL against
which all plant extracts were compared. All the plant extracts in the
study, except the three Aloespecies extracts, the two Bulbine species ex-
tracts, as well as extracts of H. limifolia,M. plumbea and Z. aethiopica
showed significantly good bioactivity at low concentrations. Tetradenia
riparia plant part extracts ranged from 3.55 to 8.50 μg/mL, H.
aethiopicum leaf extract at 4.45 μg/mL and E. autumnalis plant extracts
from 6.73 to 9.52 μg/mL and Z. aethiopica extract at 9.05 μg/mL for the
LOX inhibitory activity. These results indicate significant positive anti-
inflammatory activity, which are far more active than the positive con-
trol. Values greater than 100 μg/mL indicate less activity while those
lower than the standard control values are considered to be excellent.
A study on E. autumnalis leaves detected between 80 and 90% inhibi-
tion which is high activity for COX-1 inhibition in vitro with plant lectins
contributing to the anti-inflammatory properties (Gaidamashvilli and
Van Staden, 2006). Fawole et al. (2009) reported A. ferox leaves as hav-
ing high COX-2 anti-inflammatory activity. The LOX group of enzymes
play an important role in many inflammatory disorders (Chedea and
Jisaka, 2005; Scheinder and Bucar, 2005). Hypericum species have
been reported by various researchers as having positive antimicrobial
activity, presence of phenolic compounds and terpenoids and in vivo
wound healing activity in rats (Mukherjee et al., 2003) comparable to
the effects of a standard allopathic drug called nitrofurazone ointment.
Zantedeschia aethiopica is known for its sterols and triterpenoids
which may be attributable to its anti-inflammatory activity (Van Wyk
et al., 2009). Tetradenia riparia is one of the extensively utilised and
widespread medicinal plants in Rwanda and various new bioactive sub-
stances were isolated from its leaves including a diterpene diol with
high antimicrobial activity (Van Puyvelde et al., 1986). In M. plumbea
extracts, the flavonoid content may be the reason for its anti-inflamma-
tory properties and usage by traditional healers (Dyson et al., 1998; Van
Wyk et al., 2009). In a South African study, researchers have reported H.
limifolia as having good antimicrobial activity(Coopoosamy and Naidoo,
2011). Another study on E. autumnalis by Masondo et al. (2014),re-
ported its ethnopharmacological potential. Van Wyk et al. (2009) re-
ported the presence of lectin-like proteins with anti-inflammatory
activity in Eucomis species, with the bulb having significant COX-2 in-
hibitory action (Taylor and Van Staden, 2001) and triterpenoids benefi-
cial in wound healing therapy.
The need for conservation of these plants is critical as trade and de-
mand increase (Mander, 1997; Dold and Cocks, 2002). Bulbine species,
E. autumnalis,H. limifolia are some of the over-harvested medicinal
plants in the Eastern Cape while in KwaZulu-Natal H. aethiopicum,E.
autumnalis,M. plumbea and H. limifolia are in great demand. Eucomis
species in Limpopo Province is also one of eight most frequently traded
medicinal plants (Moeng and Potgieter, 2011). According to a recent re-
port on a wide range of South African plants by Williams et al. (2013),
the usage of medicinal plants that are endangered and threatened in-
clude all species of Haworthia,Aloe,Eucomis and Tetradenia. It is due to
Fig. 1. Percentages of cellviability withMTT assay at different concentrationsof plant extracts.1 –Aloe arborescensleaf, 2 –Aloe aristataleaf, 3 –Aloe ferox leaf, 4 –Bulbine frutescensleaf, 5 –
Bulbine frutescens root, 6 –Bulbine natalensis leaf, 7 –Bulbine natalensis root, 8 –Eucomis autumnalis leaf, 9 –Eucomis autumnalis bulb/root, 10 –Haworthia limifolia leaf, 11 –Hypericum
aethiopicum leaf, 12 –Merwilla plumbea leaf, 13 –Merwilla plumbea bulb, 14 –Merwilla pl umbea root, 15 –Tetradenia riparia leaf, 16 –Tetradenia ripari a stem, 17 –Zantedeschia
aethiopicum leaf, 18 –Zantedeschia aethiopicum stem.
Table 2
IC
50
(μg/mL) levels detected for Lipoxygenase in the different plant extracts.
Plant extracts IC
50
(μg/mL)
Aloe arborescens leaves N100
Aloe aristata leaves N100
Aloe ferox leaves N100
Bulbine frutescens leaves N100
Bulbine frutescens roots 81.54 ± 6.76
Bulbine natalensis leaves
a
6.93 ± 0.28
Bulbine natalensis roots 98.54 ± 2.10
Eucomis autumnalis leaves
a
6.73 ± 0.11
Eucomis autumnalis bulbs/roots
a
9.52 ± 0.11
Haworthia limifolia leaves N100
Hypericum aethiopicum leaves
a
4.45 ± 0.23
Merwilla plumbea leaves 32.57 ± 0.37
Merwilla plumbea bulbs 64.95 ± 3.40
Merwilla plumbea roots N100
Tetradenia riparia leaves
a
8.50 ± 0.44
Tetradenia riparia stems
a
3.55 ± 0.11
Zantedeschia aethiopica leaves N100
Zantedeschia aethiopica stems
a
9.05 ± 1.61
Quercetin 15.91 ± 3.02
a
Bold indicates significantly excellent plant extracts with lipoxygenase
content.
5S. Ghuman et al. / South African Journal of Botany xxx (2019) xxx
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demands for medicinal use, marketability and export that lead to exten-
sive harvesting pressures in the field to the extent that some of these
plants can be reduced to possible total extinction and are currently on
the red data list in South Africa. The education of people towards effec-
tive conservation is essential for sustainability (Williams et al., 2013).
This study may contribute to overcoming the conservation concerns
for these species. The ethno-pharmaceutical activities of the various
plant parts tested can be usedfor conservation information through ev-
idence-based systems. Plant protection, promotion and education with
scientific evidence is essential for sustainability and the conservation
of red data listed plants in South Africa.
The LOX enzyme is considered to produce prostaglandins in acute
inflammation (Vane and Botting, 1987; Vane and Botting, 1995; Vane
et al., 1998). Research showed that in some muscles and tissues such
as the reproductive organs of the female, brain, placenta, kidneys, the
enzyme is manufactured at a consistent rate, and synthesised
prostanoids are responsible for regulation and homeostasis in these
muscles and tissues (Hinz and Brune, 2002; Mitchell and Warner,
2006). Selective inhibition of some anti-inflammatory compounds are
the most favourable because they diminish the detrimental side effects
associated with inhibition. Theextracts with moderate activity are pref-
erable to use rather than the ones with high activity. Prolonged use of
plant extracts with high inhibition activity may lead to the expression
of damaging symptomatic side effects. The plant extracts that weresig-
nificantly positive for both NO and LOX screening for anti-inflammatory
activity compared to quercetin include T. riparia,E. autumnalis,H.
aethiopicum and H. limifolia.TheIC
50
values for the NO and the LOX in-
hibition in plants like T. riparia and H. aethiopicum in particular had sig-
nificant positive outcomes in both assays. Tetradenia riparia and H.
aethiopicum are the two plant species which also showed consistent
skin and wound healing properties.
3.3. 2, 2-Diphenyl-1-picryhydrazyl (DPPH)
The EC
50
of plant extracts with bold values (μg/mL) (Table 3)are
considered strong DPPH radical scavengers. The effective concentra-
tions at EC
50
were determined and compared to ascorbic acid as a pos-
itive control (0.070 μg/mL)
.
The plant extracts with significantly high
DPPH scavenging activity with lower EC
50
than the control were A.
arborescens leaf (0.043 μg/mL), B. frutescens leaf (0.053 μg/mL), B.
natalensis root (0.006 μg/mL) and E. autumnalis root (0.062 μg/mL).
The lower the EC
50
value, the more speedily the DPPH radical was light-
ened; therefore, the more powerful the antioxidant. The results indicate
that even at lower concentrations, these extracts maintained excellent
antioxidant activity. The activity varied markedly between the various
plant parts with leaf and root extracts generally showing the strongest
radical scavenging activity in most plant species tested. The metal che-
lation, reducing power and radical scavenging (DPPH) effects as well
as those events that are destructive to active oxygen groupings such
as the hydroxyl radical, superoxide anion radical and hydrogen perox-
ide are widely used as antioxidants (Sharma and Bhat, 2009). DPPH is
commonly known as a radical and a trap (“scavenger”) for other radi-
cals. The rate of reduction of a chemical reaction when one adds DPPH
is a good indication of the sudden changes in nature of the radicals in
the reaction (Sharma and Bhat, 2009).
3.4. β-Carotene linoleic acid model system (CLAMS)
The ORR values (Table 3) less than those of butylated hydroxytolulene
(BHT) value of 0.232 and recorded in bold are considered as excellent po-
tent antioxidants. The percentage activity of antioxidants based on the
average proportion of heat-induced β-carotene bleaching was high for
several of the tested plant extracts ranging from 29% to 96% relative to
76% BHT standard for the CLAMS assay. In order to reach 50% quenching
activity, lower concentrations of plant extracts were seen to be greater
than that of the control value of 76%. The lowest activity was 29%
recorded from M. plumbea root extract. The medicinal plant extracts
with strong antioxidant activity included A. ferox leaf extract, B. frutescens
leaf extract, B. frutescens root extract, B. natalensis leaf extract, B. natalensis
root extract, E. autumnalis leaf extract, H. limifolia leaf extract, H.
aethiopicum leaf extract, T. riparia leaf extract, Z. aethiopica leaf and Z.
aethiopica stem extracts. The extracts from the A. arborescens leaf, B.
frutescens leaf, B. natalensis root, E. autumnalis root had significant antiox-
idant activity for DPPH. In addition, A. ferox leaf extracts, B. frutescens leaf
and root extracts, B. natalensis leaf and root extracts, E. autumnalis leaf ex-
tracts, H. limifolia leaf extracts, H. aethiopicum leaf extract, T. riparia leaf
extract, Z. aethiopica leaf and stem extract were significant for the
CLAMS model. The extracts from E. autumnalis root for DPPH were
0.062 μg/mL and the leaf extracts had an ORR of = 0.197. The plant ex-
tracts for H. limifolia (ORR 0.184), H. aethiopicum (ORR 0.175), T. riparia
(ORR 0.159) and Z. aethiopica (ORR leaf extract 0.138, stem extract
0.075) also exhibited high antioxidant activity for the CLAMS assay in re-
lation to the controls (DPPH 0.07 μg/mL ORR 0.232) respectively. Some
studies have found that polyphenol concentrations found in some plant
extracts are related to the observed antioxidant activities. Dall'Agnol
et al. (2003),Avato (2005),Suntar et al. (2010) reported on the medicinal
use of Hypericum species as a balm with unique wound healing properties
and also effective against stings and bites. These authors reported that
Hypericum is a wound herb that healed bruises, opened obstructions, dis-
solved swellings, and closed up the lips of wounds, sores and for stings
and bites. The plant is also known for its antimicrobial activity and that
it contains hyperforin and hypericin. According to various researchers,
many of the active constituents in Hypericum species are polyphenols
like flavonoids, phenolics and tannins as well as conjugated
phloroglucinol derivatives and benzopyrans (Dall'Agnol et al., 2003;
Mukherjee et al., 2003; Avato, 2005; Suntar et al., 2010). Hypericum
aethiopicum exhibited significant antioxidant activity while Z. aethiopica
has been screened for its active compounds and found to contain α-
linoleic acid, a number of phenylpropanoids and triterpenoids, sterols
and lignans (Van Wyk et al., 2009).
Table 3
Antioxidant activity of 19 therapeutic plant species used for wound healing and skin dis-
orders in KZN, South Africa as evaluated by the β-carotene linoleic acid models and the
DPPH scavenging assay.
Antioxidant activity
Plant species DPPH EC
50
(μg/mL)
CLAMS
ANT (%) ORR
Aloe arborescens leaves
a
0.043 ± 0.009 73.971± 7.437 0.260 ±0.074
Aloe aristata leaves 0.604 ± 0.059 70.299± 5.509 0.297± 0.055
Aloe ferox leaves 0.273 ± 0.091 87.594± 1.778
a
0.124±0.018
Bulbine frutescens leaves
a
0.053 ± 0.015 91.354 ±5.191
a
0.086±0.052
Bulbine frutescens roots 1.309 ± 0.065 78.372± 4.603
a
0.216±0.046
Bulbine natalensis leaves 0.601 ± 0.012 96.187 ±2.751
a
0.038±0.028
Bulbine natalensis roots
a
0.006 ± 0.000 80.833± 1.536
a
0.192±0.015
Eucomis autumnalis leaves 2.160 ± 0.139 80.266 ±0.890
a
0.197±0.009
Eucomis autumnalis roots
a
0.062 ± 0.029 71.982± 1.467 0.280 ±0.015
Eucomis autumnalis bulbs 0.897 ± 0.112 67.172± 0.767 0.328 ± 0.008
Haworthia limifolia leaves 0.300 ± 0.023 81.584± 0.325
a
0.184±0.003
Hypericum aethiopicum
leaves
0.777 ± 0.071 82.468± 0.338
a
0.175±0.003
Merwilla plumbea leaves 0.258 ± 0.025 58.271 ±4.922 0.417 ±0.049
Merwilla plumbea bulbs 0.322 ± 0.031 68.952± 2.161 0.310± 0.022
Merwilla plumbea roots 1.179 ± 0.020 29.012 ±0.671 0.709 ±0.007
Tetradenia riparia leaves 5.531 ± 0.321 84.055 ±
13.620
a
0.159±0.136
Tetradenia riparia stems 2.918 ± 0.016 75.573± 3.927 0.244± 0.039
Zantedeschia aethiopica
leaves
1.838 ± 0.189 86.216± 3.784
a
0.138± 0.038
Zantedeschia aethiopica
stems
0.652 ± 0.090 92.469± 0.655
a
0.075± 0.007
Ascorbic acid 0.070± 0.010
BHT 76.727± 6.171 0.232 ±0.062
a
Bold indicates the plant extracts with significant antioxidant activity.BHT –butylated
hydroxytolulene;DPPH –2,2-diphenyl-1-picryhydrazyl;CLAIMS–β-Carotene linoleicacid
model system; ORR –Oxidation reduction rate.
6S. Ghuman et al. / South African Journal of Botany xxx (2019) xxx
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3.5. Ferric-reducing antioxidant power (FRAP)
Fig. 2 represents the capacity of the plantextracts at variableconcen-
tration ranges to reduce Fe
3+
solution. Fig. 2A–C indicate an increase in
the absorbance as the concentration levels of the extracts were in-
creased. All the plant extracts showed some chelating ability at concen-
trations below 0.1 mg/mL comparable to that of the ascorbic acid
control. Tetradenia riparia, popular for its medicinal use in Rwanda has
been screened by Van Puyvelde et al. (1986) for many active
diterpenediols. Merwilla plumbea is rich in homoisoflavones, saponins
and glycosides (Van Wyk et al., 2009) and the plant extracts are com-
monly used for wound healing and skin disorders and are also reported
for their antimicrobial and anti-inflammatory properties (Van Wyk
et al., 2009). Consistent to these findings, the same extracts, showed sig-
nificant antioxidant activity in this study. As can be seen in Fig. 2A–C, all
19 extracts tested in this study showed some degree of antioxidant ac-
tivity. Of significance, with higher absorbance are Merwilla plumbea
(0.65), Tetradenia riparia (0.6) and the Aloe species (0.75–0.84) at 1
mg/mL. The other tested medicinal plant extracts yielded absorbance
ranges from 0.24 to 0.57 at the same concentration of 1 mg/mL. For ef-
fective wound healing and dermatological conditions, plant extracts
with higher antioxidant activity and the capacity to be effective anti-in-
flammatory agents in the healing process are important attributes.
3.6. Protein precipitation/binding assay
The protein binding capacity of the 13 most active plantextracts are
presented in Table 4. Various levels of protein precipitation capacity
were reported and are indicated in the following ranges of scales from
70–100% high, 40–70% moderate, 20–40% low and 0–20% indicating in-
significant activity (Ndhlala et al., 2014). Haworthia limifolia extract ex-
hibited high affinity for protein (83%) while moderate affinity was
found in E. autumnalis and B. natalensis and the activity was either low
or insignificant in the rest of the tested extracts. The healing of wounds
is a highly intricate physiological development and multiple overlying
phases range from formation of granular tissue, inflammation, inhibi-
tion of microbial infections and re-epithelialisation, extracellular matrix
formation and remodelling of the wounded area or corrective activity at
the damaged site (Perini et al., 2015). Tissueregeneration due to pheno-
lic compounds is reported in superficial skin, wound and burn healing
combined with antimicrobial and antioxidant capacities (Bruneton,
1995; Luseba et al., 2007). Phenols havehydroxyl groups that are hydro-
gen donors and form very strong hydrogen bonds with the proteins par-
ticularly the carboxyl groups. High protein affinity or binding capacity
occurs when the phenols which are small enough to penetrate inter-
fibrillar peptide chains at many positions on the molecules result in
the formation of a film that becomes a physical barrier which is very im-
portant in the wound healing process. This capacity extends to bonding
with microbial cell walls causing inhibition (Mulaudzi et al., 2012).
There are also adverse effects of protein binding affinity where phenols
rich in tannins interact with protein uptake in the mammalian physio-
logical processes and precipitate functional enzymes for biochemical
metabolism hence causing a reduction in availability of nutrients an d ef-
ficacy and value of the medicinal plants. Van Wyk et al. (2009) reported
that the presence of triterpenoids may account for this species' wound
healing capacity. The plant extracts showed moderate protein binding
capacity and good antioxidant activity. Haworthia limifolia has a very
high protein binding capacity of 83% and good antioxidant ability. A
study by Coopoosamy and Naidoo (2011) reported significant antimi-
crobial activity for H. limifolia extracts and the species is known to con-
tain significant amounts of phenolics. However, more research on this
plant is necessary. Other than these six significant antioxidant and/or
protein-precipitating active plant extracts (M. plumbea,T. riparia,E.
autumnalis,H. limifolia,H. aethiopicum and Z. aethiopica), all Aloe and
Bulbine species presented throughout the screening showed moderate
protein binding capacity and good antioxidant activity.
Tannins are a form of polyphenolic compounds with high molecular
weight protein complexes. There are two groups of tannins formed by
their structural type variances and include the condensed tannins and
the hydrolysable tannins. Tannin quantification method is based on
their chemical capacity or their capability to form bonds with protein
substrates. Tannin–protein complexes (tannins in the plant extract
and the protein, bovine serum albumin) are the basis used to determine
protein precipitable phenolics (Ndhlala et al., 2015). The ferric chloride
assay for total phenolics determines the tannins present in the complex.
Measurements done spectrophotometrically will indicate when iron
complexes form with phenols to give a pink chromophore. The five me-
dicinal plants mentioned had a consistent pattern of significant activity
throughout this study.
4. Conclusions
Developing safe and effective anti-inflammatory agents from medici-
nal plants showing LOX and COX-2 inhibition are acknowledged as safer
Fig. 2. Ferric-reducingpower (FRAP) of 19 medicinal plantextracts used forskin disorders
and wound healing in South Africa. (1) Aloearborescens leaf, (2) Aloearistata leaf, (3) Aloe
ferox leaf,(4) Bu lbine frutescens leaf, (5) Bulbine frutescensroot, (6) Bulbine natalensis leaf,
(7) Bulbine natalensis root, (8) Eucomis autumnalis leaf, (9) Eucomis autumnalis root, (10)
Eucomis autumnalis bulb, (11) Haworthia limifolia leaf, (12) Hypericum aethiopicum leaf,
(13) Merwilla plum bea leaf, (14) Merwilla plumbea bulb, (15) Merwilla plumbea root,
(16) Tetradenia riparia leaf, (17) Tetradenia riparia stem, (18) Zantede schia aethiopica
leaf, (19) Zantedeschia aethiopica stem.Values represent mean ± standard error (n = 3).
7S. Ghuman et al. / South African Journal of Botany xxx (2019) xxx
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extracts used to trea..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.07.013
medicines with minimum side effects in vivo. A number of the plant ex-
tracts screened in this study exhibited some good anti-inflammatory ac-
tivity, a promising prospect for the development of anti-inflammatory
agents. Coupled with the excellent antioxidant activities displayed by
some of the extracts in this study using different mechanistic models,
the good anti-inflammatory activities makes excellent a combination
that assist in various processes of wound healing. The plants screened
in this study are utilised by traditional healers as management recipes
or natural resource for healing wounds and skin disorders and the results
of this study may well lend support to that credence. The mode of action
for the dermatological use of medicinal plants is sometimes determined
by their phenolic content, positive anti-inflammatory, antioxidant activ-
ity and protein interaction properties. These are complex yet intricate
pathways, each contributing a part to the whole or bigger picture in the
important role medicinal plants have to play in traditional health care.
Medicinal plants may not display activity at one pharmacological site
but may act at several potential targets, hence the various biological as-
says assist with proper evaluation of the mode of action of the selected
medicinal plants. Oxidative damage is key to accelerated pathogenesis
in numerous human diseases and natural therapies particularly from
phenolic compounds demonstrating good antioxidant and anti-inflam-
matory activity and many of the plant extract results as discussed are in-
dicative of these medicinal and healing capacities. Overall, the study
results do present some valuable anti-inflammatory and antioxidant ac-
tivities in a number of the selected medicinal plants that can be exploited
for the healthcare benefit of humankind. The results lend scientific cre-
dence in support of the traditional medicinal use particularly on Aloe
and Bulbine species. In addition, the use of E. autumnalis,H. limifolia,H.
aethiopicum,T. riparia and Z. aethiopica as antioxidant agents for treating
skin disorders and for wound healing is somewhat observed through the
the results of this and other previous research. The moderate to good pro-
tein binding capacity exhibited by some of the tested medicinal plants
could be used as a predictive wound healing model for these medicinal
plants. Having considered the results and the relationship with the anti-
oxidants, the following medicinal plants showed a correlation that was
significant: the Aloe species, B. frutescens,B. natalensis and H. aethiopicum,
H. limifolia and Z. aethiopica. Further work on the isolation, identification
and characterisation of the biologically active compounds responsible for
these events are necessary. Once isolated the active compounds can fur-
ther be used to determine and examine the mechanism of activity. The
overall results indicate that plant extracts do have the valuable capacity
and potential to be used in wound healing and skin care management.
Declaration of Competing Interest
The authors declare no conflict of interest.
Acknowledgements
The University of KwaZulu-Natal and the National Research Founda-
tion (NRF) of South Africa are gratefully acknowledged for financial
support. The Ethekwini Municipality staff at Silverglen Nursery in
Chatsworth Durban are thanked for providing plant material used in
this study.
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Table 4
Protein-precipitating capacity as a wound healing model of phenolic-rich methanolic medicinal plant extracts from KwaZulu-Natal, South Africa.
Protein-precipitating capacity
Plant species 1 2 3 4 5 6 7
Protein-precipitating phenolics(x)* 11.58 ± 0.99 17.69 ± 0.35 10.83 ± 1.87 18.22 ± 0.39 97.82 ± 1.97 3.44 ± 0.12 9.74 ± 0.45
Total phenolics (y)* 76.24 ± 2.72 64.64 ± 1.46 76.11 ± 0.89 66.71 ± 0.52 118.30 ± 3.44 16.68 ± 0.05 20.04 ± 1.21
Protein-precipitating capacity (%) 15.19 ± 0.71 27.39 ± 1.15 14.21 ± 2.29 27.31 ± 0.36 82.71 ± 0.74 20.62 ± 0.79 48.91 ± 5.21
Plant species 8 9 10 11 12 13
Protein-precipitating phenolics(x)* 2.77 ± 0.04 2.85 ± 0.17 3.24 ± 0.46 4.66 ± 0.25 3.96 ± 0.18 3.91 ± 0.25
Total phenolics (y)* 5.44 ± 0.08 7.41 ± 0.02 45.15 ± 1.12 30.11 ± 0.79 23.93 ± 0.06 11.87 ± 0.22
Protein-precipitating capacity (%) 50.87 ± 0.02 38.51 ± 2.43 7.15 ± 0.84 15.46 ± 0.43 16.53 ± 0.73 32.93 ± 1.46
1–Aloe arborescens leaf,2 –Aloe aristata leaf,3 –Aloe ferox leaf, 4 –Hypericum aethiopicum leaf,5 –Haworthia limifolialeaf, 6 –Merwillaplumbea leaf, 7 –Bulbine natalensisbulb, 8 –Eucomis
autumnalis root, 9 - Eucomis autumnalis bulb, 10 –Tetradenia riparia leaf, 11 –Eucomis autumnalis leaf, 12 –Zantedeschia aethiopica leaf, 13 –Bulbine frutescens leaf.
x* and y* are the curve slopes (mg phenolics precipitating/mg plant extracts) representative of the protein-precipitating and the phenolic totals in the extracts respectively.
8S. Ghuman et al. / South African Journal of Botany xxx (2019) xxx
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