21 | P a g e
Evaluation of the Antimicrobial and Phytochemical Properties
of Oil from Castor Seeds (Ricinus communis Linn)
Momoh, A.O*, Oladunmoye, M.K. and Adebolu,T.T.
Department of Microbiology,Federal University of Technology, Akure, P.M.B 704,Akure,Nigeria.
*Corresponding author’s Efirstname.lastname@example.org
The antimicrobial activity of the essential oil of castor (Ricinus communis) seeds extracted using soxhlet extractor in 98% n-
hexane was assessed using in-vitro assay. Twenty microorganisms made up of fourteen bacteria and six fungi were used in
the bioassay. Comparatively, bacteria were found to be more susceptible than fungi. The minimum inhibitory concentration
(MIC) of the extract was found to range between 6.25 mg/ml and 12.50 mg/ml for bacteria while that of fungi ranged from
12.50mg/ml to 25.00mg/ml. Comparison of the antimicrobial efficacy of the extract and commercial antibiotics showed that
the latter were more potent against the test organisms with the exceptions of erythromycin, ampiclox and rifampin group for
Gram positive organisms and, septrin and ceporex group for Gram negative organisms respectively. The quantitative
phytochemical screening showed that tannin, phenol, alkaloid, phytate, oxalate, saponin, cyanogenic glycoside and flavonoid
were present in a decreasing order. The spectrophotometric data of the extract using ultraviolet radiation, infrared and H-
NMR as well as carbon 13 NMR showed the presence of various compounds such as cineole, 2- octanol, terpenene -4-ol,
limonene, sabinene, pinene, terpinene, and methyl groups in the oil.
Key words: antimicrobial, phytochemicals, castor oil, microorganisms.
The oils of medicinal plants have been used for treatment of various ailments since men learnt the
art of extraction . Clove oil for instance has been used for dental pain as an anodyne (painkiller),
as antihelmintic and as aromatherapy when warming of the digestive system is needed as far back
as 1721 BC .
Castor plant, Ricinus communis, is a species of flowering plant in the spurge family, Euphorbiaceae.
Its seed is the castor bean which, despite its name, is not a true bean. Castor plant is indigenous to
the southeastern Mediterranean Basin, Eastern Africa, and India, but is widespread throughout
tropical regions . Although monotypic, the castor oil plant can vary greatly in its growth, habitat
and appearance. It is a fast-growing, suckering perennial shrub which can reach the size of a small
tree (around 12 metres / 39 feet). If sown early, under glass, and kept at a temperature of around
20 °C (68 °F) until planted out, the castor oil plant can reach a height of 2–3 metres (6.6–9.8 ft) in a
year. The flowers are borne in terminal panicle-like inflorescences of green or, in some varieties,
shades of red. The oil from the castor seed is colourless or faintly yellow, almost odorless, viscid
liquid, having a taste at first bland but subsequently avid and nauseating. It is fixed and dries very
slowly, having a specific gravity, 0.958. It is slightly dextrorotatory, about + 4o 301. It has a
refractive index, 1.4790 to 1.4805 and solidifies at -10o C to - 18oC. Its acidity is expressed as oleic
acid which is 1.5 percent. The oil extracted from the seed have been used in small doses in clinical
setting for numerous medical conditions such as liver and gallbladder disturbances, abscesses,
headaches, appendicitis, epilepsy, hemorrhoids, constipation, diarrhea, intestinal obstructions, skin
diseases, hyper activity in children and to avert threatened abortion in pregnant women [4,5,6].
Traditionally, the Ebira people in Kogi State of Nigeria use it for skin diseases, purgative, heal
irritated or inflammed nipples and to aid delivery in delayed expectant mothers. Although, much
has been documented on the uses of castor oil, there is no report on its antimicrobial activity. This
study therefore was designed to evaluate the antimicrobial and phytochemical properties of castor
MATERIALS AND METHODS
Bulletin of Environment, Pharmacology and Life Sciences
Online ISSN 2277 – 1808
Bull. Environ. Pharmacol. Life Sci.; Volume 1  September 2012: 21 - 27
© All Rights Reserved Academy for Environment and Life Sciences, India
22 | P a g e
The castor plant seeds used in this study were the white variety of the Ricinus communis L. This
was collected from a farm at Eika village, Okene, Kogi state, Nigeria.
Microorganisms used in the bioassay
The microorganisms used were obtained from the Microbiology Department, University of Ibadan
Teaching Hospital, Ibadan, Oyo State, Nigeria. The Gram positive bacteria used include:
Staphylococcus aureus, Bacillus cereus, Streptococcus faecium, Streptococcus pyogenes, Bacillus
marcesene and Streptococcus mitis while the Gram negative used were Escherichia coli,
Pseudomonas aeruginosa, Shigella dysenteriae, Salmonella enteritidis, Salmonella typhimurium,
Klebsiella pneumoniae and Proteus vulgaris. The fungi used are Fusarium oxysporum, Penicillium
oxalicum, Candida albicans, Penicillium cinirium, Aspergillus flavus and Aspergillus niger.
Extraction of oil from the seeds
The soxhlet extraction of castor oil from 500g of castor seeds using one litre of n-hexane was done
according to the method of Odugbemi, .
Antimicrobial sensitivity testing of the extracted oil.
With the aid of a sterile pipette, 1ml of 18 hour old peptone broth culture of the test organism
cultured at 37˚C was added to 20ml sterile molten NA and PDA respectively which had already
cooled to 45oC. This was well-mixed and allowed to set. With the aid of sterile 4mm cork borer, 3
wells were bored on the agar surface. To each of the 2 wells was added 2 drops (0.4ml) of the oil
using Pasteur pipette aseptically. The well in the center was filled with same amount of sterile
distilled water to serve as control.
The Optu-sensitivity discs were used for this assay. The discs were picked with sterile forceps and
placed on the surface of the solidified NA previously seeded with 106 an overnight bacterial culture.
The plates were incubated at 37oC for 24hours. The plates were then examined for clear zones of
inhibition of bacterial growth around the discs. The procedure was repeated for test fungi. The
antimycotic drug used was fulcin and incubation was done at 25oC for 5 days. The results were
then compared with that of oil extract.
Minimum inhibitory concentration determination
The minimum inhibitory concentration (MIC) was determined using the method described by
Olutiola et al. . Standardization of inoculum size was determined using spectrophotometer and
the plate count method. Different concentration of the extract were prepared at 25, 12.5, 6.25 and
3.1mg/ml, and 5ml of an 18hour old culture of the organism was pipetted into test tubes. Using
sterile syringe, 1ml of the different concentrations of the extract was poured into the broth culture
and incubated for 24hours at 37o C. The tubes were checked for growth as indicated by turbidity
and confirmed with the aid of spectrophotometer. The least concentration at which inhibition was
noticed was taken as the minimum inhibitory concentration (MIC).
Basic phytochemical analysis was carried out to determine the bioactive ingredient present in the
extract and their percentages. The standard methods of analysis of analytical methods committee
of Royal Society of chemistry, (2002) were adopted to determine cyanogenic glycosides, tannin,
saponin, oxalate, phytate, phenol, alkaloid and flavonoid.
Nuclear magnetic resonance, infra-red and ultra violet analyses of the oil extract was carried out in
Central Science Laboratory, Obafemi Awolowo University, Ile-Ife, Osun State of Nigeria according to
standard methods of analysis of analytical methods committee of Royal Society of chemistry,
The data gathered were processed using descriptive one way analysis of variance, SPSS Version 10
Microsoft Windows 7. The Duncan Multiple Range Test was used as a follow up test.
RESULTS AND DISCUSSION
In vitro inhibitory effect of castor oil on test organisms
The extracted castor oil inhibited the growth of all the test organisms. Among the Gram positive
bacteria, Staphylococcus aureus was the most sensitive and Micrococcus luteus was the least
sensitive with zones of inhibition of 7.00 mm and 2.50 mm respectively. Among the Gram negative
23 | P a g e
bacteria, Escherichia coli was the most sensitive and Proteus vulgaris was the least sensitive with
zones of inhibition of 6.50 mm and 3.00 mm respectively. Among the fungi, Fusarium oxysporum
was the most sensitive while Aspergillus niger was least sensitive to the oil with zones of inhibition
of 4.00 mm and 1.50 mm respectively. Generally, the oil was more effective on bacteria than fungi
as shown in Table 1.
Table 1: Sensitive pattern of selected microorganisms to the extracted castor oil
Zone of inhibition
Antibiotic sensitivity assay
The result of the antibiotic sensitivity assay on Gram positive bacteria is shown on figure 1. Some of
the antibiotics were found to have higher antimicrobial activities on the organisms than the castor
oil. Rifampin, lincomycin and floxapen had lower antimicrobial activities on the organisms than the
extract while streptomycin, norfloxacin, chloramphenicol, gentamycin and ciproflox showed higher
antimicrobial activities than that of the extract. Erythromycin and ampiclox had approximately the
same effect as that of the extract on the test bacteria.
On the Gram negative bacteria, tarivid, streptomycin, nalidixic acid, gentamycin, augmentin and
ciproflox showed higher antimicrobial activities than the extract. The result also showed that some
of the test organisms were resistant to ampicillin, peflacine and ceporex making the extract more
effective than the antibiotics as shown on figure 2.
Penicillum cinirum was most sensitive while Candida albicans was least sensitive to Fulcin with
zones of inhibition of 12 mm and 4 mm respectively. However, in general, the antifungal agent
(Fulcin) was more effective than the extract as shown in figure 3.
Minimum inhibitory concentration (MIC)
All the Gram positive bacteria had a constant MIC value (12.50 mg/ml) except Staphylococcus
aureus that had a lower value of 6.25 mg/mL. The MIC for the fungal group were however higher.
Aspergillus flavus, Aspergillus niger and Penicillium cinirium had 25.00 mg/mL as their MIC while
Candida albicans, Fusarium oxysporum and Penicillium oxalicum had 12.50 mg/mL.
24 | P a g e
Figure 1: Bar –chart showing the comparison of the activities of extract and standard antibiotics
on Gram positive bacteria.
Keys S = Streptomycin, NB = Norfloxacin, CH = Chloramphemicol, CPX = Ciproflox, E = Erythromycin, LC = Lincocin, CN = Gentamycin,
APX = Ampiclox, RD = Rifampin, FLX = Floxapen
Figure 2: Comparative antimicrobial activities of castor oil extract and standard antibiotics on Gram
negative bacteria. Keys S = Streptomycin, PN = Ampicillin, OFX = Tarivid, NA = Nalidixic acid, PEF = Peflacine,
CN = Gentamycin, AU = Augmentin, CPX = Ciproflox, SXT = Septrin, CEP = Ceporex.
S NB CH CPX E LC CN APX RD FLX CO
Antibiotics and castor oil extract
Zo n es of in hibi ti on ( mm )
S PN OFX NA PEF CN AU CPX S XT CEP CO
Antibiotics and castor oil extract
Zones o f inhibit ion (mm)
25 | P a g e
Figure 3: Comparative antimicrobial activities of extract and standard antifungal agent on selected
Phytochemical screening of the extract for the presence of bioactive compounds revealed the
presence of tannin, saponin, alkaloid, phytate, oxalate, flavonoid, cyanogenic glycoside and phenol.
The most abundant phytochemical present in the extract was tannin (0.35 %) while the least was
observed in flavonoid and cyanogenic glycoside (0.03 %) each.
The following absorptions were observed: 220 nm, 226 nm and 236 nm with 226 nm being the
lambda maximum. These absorptions may be as a result of conjugated double bond that is present
in some of the fatty acid present. Minor absorptions were observed at 268 and 280 nm
The Infrared result, at different wave number per centimeter and their probable functional groups
are shown below in Table 2.
Nuclear magnetic Resonance Result
The result of the NMR shows different functional groups as well. The various frequencies and their
corresponding identification is shown in Table 3. The proton NMR of the extract and its
identification is shown in Table 4.
Table 2= Infra-red result
Wave number (cm
Probable functional group
H (stretch), COOH, NH
O-H, C-H, CH2, CH3
C-H, CH2, C-O
CH2 (Stretch), C-H (bending)
C-H, C-O, C=C
C-H, CH2, C=C
C-H (stretch), CH2
Aspergillus flavus Aspergillus niger Candida albicans Fusarium
Antifungal agent (Fulcin)
26 | P a g e
Table 3: NMR frequencies and their identifications
C = O
Table 4: Proton NMR of the extract and their identifications
Proton NMR (ppm)
3.29 – 3.45
1.75 – 2.15
0.80, 0.85, 0.90, 0.98, 1.00, 1.05
Alcohols of Cineole and 2
CH = CH of Limonene, Sabinene, Pinene and
CH2 (Methylene group of the essential oil)
CH3 Signals (Methyl group of the essential oil).
The findings in this research work indicate that the percentage yield of the extract using 98% N-
hexane as solvent of extraction is about 20% of the total mass of the seed. This corroborate the
report of Gerhard et al,.  that the amount of volatile oil in castor beans is 20%.
From the results of this investigation, the antimicrobial activities of the extract against test
organisms highly varied. Bacteria were observed to be more sensitive than fungi. One reason for
the low susceptibility of fungi is probably their eukaryotic nature, which is responsible for their
advance cellular and molecular process, when compared to bacteria which are prokaryotic in
The susceptibility of some of the organisms used may be due to their genetic make - up and
absence of resistant transfer factor. Streptococcus species used showed moderate susceptibility to
the extract and this may be due to their ability to produce different enzymes and toxins which may
be able to degrade some of the active components of the essential oil. The Bacillus species showed
low susceptibility to the extract probably due to their ability to form spores which could have
shielded them from the extract. Fungi were less susceptible to the castor oil extract than bacteria,
however none of the fungi tested for was resistant to the extract. Though, the mechanism of action
of the extract was not studied, the presence of biologically active chemicals such as saponin, tannin,
phenol, cyanogenic glycoside and flavonoids could be responsible for the antimicrobial activity of
the oil. The presence of the various compounds revealed by the spectrophotic analysis of this
27 | P a g e
extracts shows that the antimicrobial properties of the essential oil could be traced to these
compounds. According to Omidbeygi et al,  and Rota et al, , the composition, structure, as
well as the functional group of an essential oil play an important role in determining its
This study has been able to show that castor oil has antimicrobial activity in addition to its
purgative, anti-inflammatory and labor inducing ability that has been documented earlier on by
many researchers. It is therefore conceivable that castor oil could be used in treating infections
caused by the test organisms used in this work in the absence of conventional therapy or
1. Dan B; Steven, C; Erich’s; Andrew, G (2004).Chinese herbal medicine: Materia Medica 3rd edition. 3:79-90.
2. Weiss, R.F. and Fintelmann, V. (2010). Herbal medicine, 2nd edition, Herbs Publisher thieme, New York, USA. 505pp
3. Phillips, R. and Martyn, R. (1999). Annuals and Biennials. London: Macmillan. P. 106. ISBN 0333748891.
4. Christopher, B. ed (1996). The Royal Horticultural Society A-Z Encyclopedia of Garden Plants. London: Dorling
Kindersley. pp. 884–885. ISBN 0751303038
5. LA Betancur-Galvis, Morales. G. E., Forero, J. E. and Roldan, J. (2009), "Cytotoxic and Antiviral Activities of
Colombian Medicinal Plant Extracts of the Euphorbia genus", Memórias do Instituto Oswaldo Cruz 97 (4): 541-546.
Retrieved through Bioline International (keywords: herpes simplex - Bioline Code: oc02103).
6. Odungbemi; T. (2006).Outline and pictures of medicinal plants from Nigeria, University of Lagos press, Yaba Lagos,
7. Olutiola, P.O., Famurewa, O., Sonntag, H.G (2000). Introduction to general Microbiology, 2nd Edition, Heidelberg,
8. Gerhard, R;keith, R.O; amram, A. (2004). Oil crops of the world – their breeding and utilization. McGraw hil, New
9. Omidbeygi, M; Barzegar M. Hamidi, 2; Naghdibadi; H. (2007). Antifungal activities of thyme, summer savory and
clove essential oils against Aspergillus flavus in liquid medium and tomato paste. Food control, 18:1518-1523.
10. Rota, C., Carraminanna, J.J., Bunillo, J. Herrera, A. (2009). In vitro antimicrobial activity of essential oils from
aromatic plants against selected food borne pathogens. Journal of food protection. 67:1252-1256.
11. Celikel, N and Kavas, G. (2003). Antimicrobial properties of some essential oils against some pathogenic
microorganisms. Czech Journal of food science. 26:174-181.
QR CODE: T100178
BEPLS ABSTRACTED AND INDEXED
Zoological Records [USA, Thompson Reuters], ISI Master Journal List,
Index Copernicus, EJournal, WorldCat, ABC Open Directory, Newjour,
Geneva Medical Foundation, Electronic Journal Library, Global
Education Index, Indiawaterportal, Valiasr, Google, Google Scholar
and listed in many more libraries.