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Topical L-Ascorbic Acid

Authors:
  • Kansas State University and North Carolina State University

Abstract and Figures

BACKGROUND: Reactive oxygen species generated by ultraviolet light result in photocarcinogenic and photoaging changes in the skin. Antioxidants protect skin from these insults. OBJECTIVE: This study defines formulation characteristics for delivering L-ascorbic acid into the skin to supplement the skin's natural antioxidant reservoir. METHODS: L-ascorbic acid or its derivatives were applied to pig skin. Skin levels of L-ascorbic acid were measured to determine percutaneous delivery. RESULTS: L-ascorbic acid must be formulated at pH levels less than 3.5 to enter the skin. Maximal concentration for optimal percutaneous absorption was 20%. Tissue levels were saturated after three daily applications; the half-life of tissue disappearance was about 4 days. Derivatives of ascorbic acid including magnesium ascorbyl phosphate, ascorbyl-6-palmitate, and dehydroascorbic acid did not increase skin levels of L-ascorbic acid. CONCLUSIONS: Delivery of topical L-ascorbic acid into the skin is critically dependent on formulation characteristics.
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© 2001 by the American Society for Dermatologic Surgery, Inc. Published by Blackwell Science, Inc.
ISSN: 1076-0512/01/$15.00/0 Dermatol Surg 2001;27:137–142
Topical L-Ascorbic Acid: Percutaneous Absorption Studies
Sheldon R. Pinnell, MD,* Huanshu Yang, MD,
Mostafa Omar, PhD,
Nancy Monteiro Riviere, PhD,
Holly V. DeBuys, MD,* Linda C. Walker,*
Yaohui Wang, MD,
§
and Mark Levine, MD
§
*
Duke University Medical Center, Durham, North Carolina,
PhytoCeuticals, Elmwood Park, New Jersey,
College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, and
§
National Institute of Diabetes & Digestive & Kidney Diseases, NIH, Bethesda, Maryland
background.
Reactive oxygen species generated by ultraviolet
light result in photocarcinogenic and photoaging changes in the
skin. Antioxidants protect skin from these insults.
objective.
This study defines formulation characteristics for
delivering L-ascorbic acid into the skin to supplement the skin’s
natural antioxidant reservoir.
methods.
L-ascorbic acid or its derivatives were applied to pig
skin. Skin levels of L-ascorbic acid were measured to determine
percutaneous delivery.
results.
L-ascorbic acid must be formulated at pH levels less
than 3.5 to enter the skin. Maximal concentration for optimal
percutaneous absorption was 20%. Tissue levels were saturated
after three daily applications; the half-life of tissue disappear-
ance was about 4 days. Derivatives of ascorbic acid including
magnesium ascorbyl phosphate, ascorbyl-6-palmitate, and dehy-
droascorbic acid did not increase skin levels of L-ascorbic acid.
conclusions.
Delivery of topical L-ascorbic acid into the skin
is critically dependent on formulation characteristics.
IN THE PRESENCE of our oxygen-rich atmosphere,
ultraviolet light generates reactive oxygen species in
skin. In addition to sunlight, other inflammatory in-
sults including smoking and pollution generate reac-
tive oxygen species. Reactive oxygen species, in turn,
cause oxidation of nucleic acids, proteins, and lipids.
Reactive oxygen species alter DNA,
1–7
as well as its
repair,
8
and trigger cytokine cascades that result in
photoaging
9,10
and photocarcinogenesis.
11
The body protects itself naturally from reactive ox-
ygen species by using antioxidants to neutralize them
before they cause damage to the skin and its compo-
nents. Vitamin C, or L-ascorbic acid, is the most
abundant antioxidant in skin.
12
Although most plants
and animals synthesize L-ascorbic acid to protect
themselves from free radical attack, a gene necessary
for its synthesis, L-gulono-
-lactone oxidase, has been
mutated in humans.
13
As a result, humans rely on di-
etary intake for their supply.
14
L-ascorbic acid is quite
water soluble and serves as the major aqueous phase
reductant in the body.
15
Since skin relies on antioxidants for protection
against reactive oxygen species, and since skin pre-
dominantly receives and must deal with the free radi-
cal assault resulting from UV light, increasing the anti-
oxidant defense of skin becomes an attractive strategy
for increased photoprotection.
16
If antioxidants could
be delivered in high concentration through the stratum
corneum barrier into the skin, then the antioxidant
protective reservoir could be increased and photopro-
tection might be enhanced. Indeed, our laboratory has
described a stable aqueous formulation of L-ascorbic
acid that gets into skin and provides photoprotection
against both UVB and UVA-psoralen phototoxicity by
a mechanism that is clearly not a sunscreen effect.
17
Moreover, we have demonstrated that topical L-ascor-
bic acid protected against UV immunosuppression and
tolerance to contact antigen in mice.
18
In order to maximize the protective effects of topi-
cal L-ascorbic acid in skin, we have undertaken this
study of formulation composition and kinetics so that
we can maximize the amount of L-ascorbic acid deliv-
ered into the skin.
Materials and Methods
L-ascorbic acid (pharmaceutical grade) was purchased from
Roche (Nutley, NJ). All concentrations of L-ascorbic acid
were made fresh and stabilized in 2% ZnSO
4
, 0.5% biofla-
vonoids, 1% hyaluronic acid, 0.1% citrate in glass-distilled
water. pH was adjusted with triethanolamine. Commercial
formulations of 13% magnesium ascorbyl phosphate (Vivi-
H. Yang, MD, N. Monteiro-Riviere, PhD, H.V. DeBuys, MD, L.C.
Walker, Y. Wang, MD, and M. Levine, MD have indicated no signifi-
cant interest with commercial supporters. S.R. Pinnell, MD is a consult-
ant for Skinceuticals (Dallas, TX). M. Omar, PhD is president of Phyto-
Ceuticals (Elmwood Park, NJ).
Address correspondence and reprint requests to: Sheldon R. Pinnell,
MD, Duke University Medical Center, Department of Medicine, Divi-
sion of Dermatology, P.O. Box 3135, Durham, NC 27707, or e-mail:
pinne002@mc.duke.edu.
138
pinnell et al.: topical l-ascorbic acid
Dermatol Surg 27:2:February 2001
fying Serum C, Dr. Mary Lupo Skin Care Products, New
Orleans, LA) and 10% ascorbyl-6-palmitate (C-Esta Serum,
Jan Marini Skin Research, San Jose, CA) were obtained
fresh from the manufacturer and opened just prior to test-
ing. Samples were tested as is; the content was not con-
firmed. Dehydroascorbic acid 1 M (17.4%) was prepared
by taking 1 ml of a 1 M ascorbate solution, adding bromine
55
l, vortexing vigorously for 30 seconds, and then imme-
diately bubbling with nitrogen for 10 minutes.
19
The institu-
tional review board of the College of Veterinary Medicine at
North Carolina State University approved the animal exper-
iments.
Experiments were conducted in white Yorkshire pigs.
The skin was shaved with an electric shaver 24 hours before
the experiment began to allow healing of any skin nicks.
Two hundred
l of formulation, the maximal volume of the
chamber, was placed under a Hill Top Chamber (Hill Top
Co., Cincinnati, OH) for 22–24 hours. The chamber is semi-
occlusive and protects the material from smearing. Although
the chamber may enhance percutaneous absorption, in sev-
eral cases in the experimental results, the baseline skin levels
of L-ascorbic acid were not increased. In some experiments
the chamber was replaced with fresh solution and changed
each day. In clinical practice, vitamin C solutions are usually
applied daily. At the end of the experiment, the formulation
was washed vigorously from the skin with water. Washed
skin was tape stripped 15 times to remove surface contami-
nation and stratum corneum. The tape strips were dis-
carded. Studies have shown that tape stripping removes the
stratum corneum layers (data not shown) and removes sur-
face radioactivity of topically applied substances bound to
the stratum corneum.
20
,
21
Full-thickness 6 mm punch biopsy
specimens of skin were taken and placed immediately into
liquid nitrogen. Tissue was shattered in liquid nitrogen and
weighed aliquots extracted and stabilized in 60% methanol,
1 mM EDTA in water, centrifuged, and kept at
70
C until
analyzed. Samples were analyzed in a blinded manner for
vitamin C by high-performance liquid chromatography
(HPLC) with coulometric electrochemical detection.
22
,
23
The
method is specific for L-ascorbic acid and has a sensitivity of
50 fmol. The results are expressed as mean
standard devi-
ation. Unless otherwise noted,
n
3. The
P
values were cal-
culated by two-tailed Student’s
t
-test with equal variance.
Results
pH
Fifteen percent formulations of L-ascorbic acid were
tested at pH levels between 2.0 and 5.0 (Figure 1). Tis-
sue levels of L-ascorbic acid were enhanced only at for-
mulation pH levels less than 3.5. The pKa for L-ascorbic
acid is 4.2. Apparently the molecule must be un-ionized
for percutaneous absorption to occur. Low pH is es-
sential for absorption and delivery is enhanced as the
pH is reduced to 2.0. The effect of the solutions on
skin pH is unknown.
Concentration
L-ascorbic acid concentrations were tested from 5 to
30.0% (Figure 2). pH was adjusted to 3.2. Tissue lev-
els of L-ascorbic acid increased and were maximal at
20%. For unknown reasons, concentration levels
higher than 20% resulted in decreased tissue levels.
Kinetics
Fifteen percent L-ascorbic acid at pH 3.2 was applied
daily for 1–5 days (Figure 3). After 3 days, tissue levels
were apparently saturated. Levels achieved were ap-
proximately 20 times normal tissue levels.
Washout
Fifteen percent L-ascorbic acid at pH 3.2 was applied
daily for 5 days to saturate skin levels (Figure 4). Skin
levels of L-ascorbic acid were then measured at daily
intervals, with no further topical application of L-ascor-
bic acid, to measure L-ascorbic acid remaining in the
tissues. Half-life of L-ascorbic acid in tissues was found
to be approximately 4 days.
Figure 1. Effect of pH on percutaneous absorption. 15% L-ascorbic
acid at different pHs were applied to pig skin for 24 hours. Skin
levels of L-ascorbic acid are expressed as mean SD (n 3). *Av-
erage (n 2).
Figure 2. Effect of concentration on percutaneous absorption.
Varying concentrations of L-ascorbic acid pH 3.2 were applied to
pig skin for 24 hours. Skin levels of L-ascorbic acid are expressed as
mean SD (n 3).
Dermatol Surg 27:2:February 2001
pinnell et al.: topical l-ascorbic acid
139
Ascorbic Acid Derivatives
Because L-ascorbic acid is an unstable molecule to
formulate for topical use, more stable derivatives of
L-ascorbic acid have been utilized in topical formula-
tions. Although esters of ascorbic acid are more stable
and readily converted to L-ascorbic acid after oral in-
gestion, it is not clear that derivatives, after topical ap-
plication, are absorbed into the skin or converted to
L-ascorbic acid after penetration. We have tested com-
mercially available high concentration formulations of
magnesium ascorbyl phosphate and ascorbyl-6-palmi-
tate to see if topical application resulted in elevated
skin levels of L-ascorbic acid (Figure 5). Neither ester
significantly increased L-ascorbic acid skin levels.
Dehydroascorbic Acid
Since dehydroascorbic acid can be enzymatically con-
verted to L-ascorbic acid in the body, we asked
whether topical dehydroascorbic acid could preferen-
tially raise skin L-ascorbic acid levels. Neither 20 mM
nor 1 M solutions of dehydroascorbic acid were effec-
tive. Skin levels of L-ascorbic acid were 7.51
3.34
pmol/mg for 20 mM dehydroascorbic acid and 8.70
2.13 pmol/mg for 1 M dehydroascorbic acid (
n
4)
and 9.24
3.55 for control skin.
Discussion
L-ascorbic acid is the most plentiful antioxidant in
body fluids
15
and in the skin.
12
It efficiently neutralizes
reactive oxygen species including superoxide anion,
24
hydroxyl radical,
25
singlet oxygen,
26
and peroxyni-
trite.
27
It is a particularly efficient antioxidant because
in one electron transfer reaction, its free radical inter-
mediate, ascorbic acid free radical, has low pro-oxi-
dant activity
28
and is enzymatically regenerated back
to L-ascorbic acid. Moreover, L-ascorbic acid’s effi-
ciency extends to lipophilic antioxidants as well; it re-
generates oxidized vitamin E molecules.
29,30
Maxi-
mum skin levels of L-ascorbic acid from ingestion are
regulated by active transport mechanisms that pre-
clude increasing levels by further ingestion.
31
In this
study we identify formulation characteristics that al-
low us to bypass these controls and increase the skin
reservoir by direct topical application.
This study reveals the critical importance of formu-
lation pH for percutaneous absorption of L-ascorbic
acid. Not until the pH was 3.5 or lower were cutane-
ous levels increased. Since the pKa of L-ascorbic acid
is 4.2, the molecule apparently must be un-ionized for
delivery across the stratum corneum barrier.
32
Percu-
taneous absorption of varying L-ascorbic acid concen-
trations formulated at acid pH increased steadily to a
maximum of 20%. Higher concentrations were less ef-
fective for unknown reasons. Daily application for 3
days of 15% L-ascorbic acid formulated at pH 3.2 re-
sulted in saturating skin concentrations of L-ascorbic
acid at more than 20 times control values. After satu-
rating the skin reservoir, the L-ascorbic acid was ap-
Figure 3. Time course of percutaneous absorption. 15% L-ascorbic
acid pH 3.2 was applied daily to pig skin for varying times. Skin
levels of L-ascorbic acid are expressed as mean SD (n 3).
Figure 4. Washout of skin L-ascorbic acid. Skin levels of L-ascorbic
acid were saturated by five daily applications to pig skin of 15%
L-ascorbic acid pH 3.2. After varying intervals skin levels of L-ascor-
bic acid were determined. Skin levels of L-ascorbic acid are ex-
pressed as mean SD (n 3).
Figure 5. Percutaneous absorption of ascorbic acid derivatives.
15% L-ascorbic acid pH 3.2 (VC-15), 10% ascorbyl-6-palmitate
(C-Esta), and 12% magnesium ascorbyl phosphate (Mag-C) were
applied to pig skin for 24 hours. Skin levels of L-ascorbic acid are
expressed as mean SD (n 10). P values are expressed versus
control. The P value of VC-15 versus each product is also 0.0005.
140
pinnell et al.: topical l-ascorbic acid
Dermatol Surg 27:2:February 2001
parently stabilized and remained in the tissue with a
half-life approaching 4 days. We have no data about
the relative distribution of ascorbic acid in the skin. A
persistent reservoir of antioxidant provides an impor-
tant and attractive photoprotection strategy when
contrasted to sunscreens which must be applied daily.
In the body both L-ascorbic acid and dehydroascor-
bic acid can be transported into cells, the latter con-
verted efficiently into L-ascorbic acid by glutathione
and enzymatic reduction.
33
L-ascorbic acid requires a
specific protein to be transported into cells. Hexose
transporters transport dehydroascorbic acid. Indeed
dehydroascorbic acid is preferentially accumulated in
comparison to L-ascorbic acid in HaCaT, a human
keratinocyte cell line.
34
Our experiments to deter-
mine whether dehydroascorbic acid was preferable to
L-ascorbic acid for topical use failed to reveal any in-
crease in skin levels of L-ascorbic acid with dehydro-
ascorbic acid.
Topical magnesium ascorbyl phosphate and ascor-
byl-6-palmitate in the tested formulations failed to in-
crease skin levels of L-ascorbic acid. Previous studies
have documented the marginal percutaneous absorp-
tion of magnesium ascorbyl phosphate;
35
as a charged
molecule, it would not be expected to traverse the stra-
tum corneum. Previous studies of ascorbyl-6-palmitate
failed to demonstrate protection against photoaging in
mouse skin;
36
in comparison, L-ascorbic acid was pro-
tective even though the formulation used was not op-
timal for percutaneous delivery. Although ascorbyl-
6-palmitate appears to readily enter skin,
36
its conversion
to L-ascorbic acid may be inefficient. Ascorbyl-6-pal-
mitate appears to remain on the extracellular surface
of cells and may not be readily converted to L-ascorbic
acid.
37
Indeed in human skin fibroblast culture 10
5
M
L-ascorbic acid, which is the physiologic concentration
in humans, stimulated cell growth, whereas similar lev-
els of ascorbyl-6-palmitate were toxic.
38
Topical antioxidants have been previously demon-
strated to be photoprotective for skin. Topical L-ascor-
bic acid has been shown to decrease UVB erythema in
pig
17
and human skin.
39
It also lessened UVA-psoralen
phototoxic injury in pig skin.
17
In hairless mice, topi-
cal L-ascorbic acid decreased photoaging changes in
human
40
and hairless mouse skin.
36
In addition, it pre-
vented UVB immunosuppression and tolerance to di-
nitrochlorobenzene (DNCB).
18
In persons with either
basal cell carcinoma or squamous cell carcinoma, se-
rum levels of L-ascorbic acid were below control lev-
els.
41
Topical
-tocopherol decreased photoinjury in
skin
36,42–47
and prevented UV immunosuppression.
45,48,49
Herbal antioxidants, including silymarin, a flavonoid
present in the thistle plant,
50
and grape seed polyphe-
nols
51
have been shown to prevent UV-induced squa-
mous cell skin cancer in mice.
Although all UV light can produce oxidative stress
in skin, UVA is more efficient. The peak UV spectrum
for generation of singlet oxygen from trans-urocanic
acid, a known photoreceptor in skin, is about 350
nm.52 The UV spectrum is similar to that previously
demonstrated to generate photoaging changes in mouse
skin.53 UVA from artificial light sources has been dem-
onstrated to generate photoaging changes in sun-pro-
tected skin.54,55 Similar changes have been demonstrated
using only long-wave UVA (340–400 nm).56 Studies in
skin cells,57,58 as well as human skin,10 implicate acti-
vation of matrix metalloproteinase by a mechanism in-
volving singlet oxygen, AP-1, and NF-B. In prelimi-
nary studies, antioxidants reverse activation of AP-1.58,59
Previous studies have demonstrated that photoaging
changes are even more pronounced in smokers than
sunbathers, and the combination of smoking and sun
exposure was most damaging of all.60 Presumably smok-
ing and UV exposure are both damaging to skin by
generating reactive oxygen species. In smokers, serum
ascorbic acid levels were reduced;61 they required an
elevated minimum daily dose of L-ascorbic acid to
keep body stores saturated.26
In addition to its antioxidant effects, L-ascorbic
acid is important for wound healing.62,63 It is essential
for collagen synthesis; in addition to its cofactor re-
quirements for lysyl hydroxylase and prolyl hydroxy-
lase,64 it stimulates transcription of collagen genes.65 It
has been used as a skin lightener; it inhibits tyrosi-
nase.66 Topical L-ascorbic acid has been reported to
be useful for healing of skin resurfaced by CO2 laser;
it reduced postlaser erythema.67 Topical L-ascorbic
acid together with 20% glycolic acid used for 3
months improved striae alba.68
Topical L-ascorbic acid provides a safe and effec-
tive supplement to normal tissue stores to enhance
photoprotection, improve wound healing, and in-
crease antioxidant defenses. Details of formulation are
essential if it is to be maximally effective. It must be
formulated at high concentration and at a pH lower
than 3.5 to be effective. After being delivered into the
skin, L-ascorbic acid is stabilized and remains in the
tissue for a period of days. Magnesium ascorbyl phos-
phate and ascorbyl-6-palmitate are not effective sub-
stitutes for L-ascorbic acid in topical formulations. Al-
though they are effective vitamin C derivatives for oral
use, they are apparently ineffective for increasing tis-
sue vitamin C levels when applied to the skin.
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... For optimal penetration to the epidermis, aqueous formulations of AA (including its sodium salt) must be at a pH < 3.5, below the pKa limit (pKa 4.2). Therefore, the ionic charge is removed, and the molecule is transported well across the SC [16][17][18]. However, skin pH is around 5.5, and topical 3-O-ethyl-L-ascorbic acid (ETVC) is a derivative of AA widely used in topical products [17,[27][28][29]. ...
... However, these incorporate polymers, resins, skin permeation enhancers or chelating agents. There are also studies on the release of ETVC or vitamin C using different solvents, enhancers, serums and polymeric hydrogels [17,18,22,27,29,37,[52][53][54][55], and there are numerous market products with vitamin C, but none involve lipidic gels without polymers, skin permeation enhancers or resins. The HG used in this study is a colloidal lipid gel formed by the aggregation of phospholipid vesicles under dilute conditions [30][31][32][33]. ...
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This study explores the incorporation of 10% 3-O-ethyl L-ascorbic acid (ETVC), a derivative of vitamin C, into two lipid gel systems: a hydrogel (HG) consisting exclusively of lipids and water and a bigel (BG) combining the hydrogel with an oleogel made from olive oil and beeswax. We investigated the ETVC release profiles from both materials using synthetic membranes and measured their permeation through porcine skin in vitro. Additionally, the interaction of these lipid gel systems with the stratum corneum (SC) was determined. Results from the release study indicate that the BG exhibited slower ETVC release compared to the HG. The permeation experiments showed that the presence of lipids in the formulations enhanced ETVC retention in the skin. The HG delivered a higher amount to the SC, while the BG achieved greater retention in the epidermis. This difference is attributed to the different lipophilic nature of each material. The structural analysis of SC lipids revealed that the organization of surface lipids remained unaltered by the application of the gels. Finally, an in vitro efficacy test in porcine skin using methylene blue indicated that our ETVC gels exhibited antioxidant activity. These findings provide valuable insights into the potential of lipid-based gels for topical applications.
... Because AA is highly unstable in aqueous conditions, minimizing the amount of water and partially replacing the solvent with polyols to prepare a stable formulation are necessary. In addition, because high concentrations of AA formulations are effective for topical absorption [54], we investigated whether the solubility of AA in polyols could be improved through the formation of THEDES. The selection of four polyols (glycerin, 1,3-butylene glycol, dipropylene glycol, and 1,3-propanediol) as the solvents evaluated in this study was motivated by the importance of these solvents in the cosmetics and pharmaceutical industries and their frequent use as solvents or surfactants in topical formulations or pharmaceutical excipients [55]. ...
... Because AA is highly unstable in aqueous conditions, minimizing the amount of water and partially replacing the solvent with polyols to prepare a stable formulation are necessary. In addition, because high concentrations of AA formulations are effective for topical absorption [54], we investigated whether the solubility of AA in polyols could be improved through the formation of THEDES. The selection of four polyols (glycerin, 1,3butylene glycol, dipropylene glycol, and 1,3-propanediol) as the solvents evaluated in this study was motivated by the importance of these solvents in the cosmetics and pharmaceutical industries and their frequent use as solvents or surfactants in topical formulations or pharmaceutical excipients [55]. ...
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L-ascorbic acid (AA), a potent antioxidant, is commonly used topically in the pharmaceutical and cosmetic fields. However, the incorporation of AA into topical formulations is difficult because of its highly unstable nature and relatively poor skin permeability. In this study, we propose an alternative strategy for improving the solubility and topical delivery of AA through its conversion to a therapeutic deep eutectic system (THEDES). AA and betaine (Bet)-based THEDESs were prepared at certain molar ratios and characterized using polarized optical microscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. Solubility tests showed that AA in the form of THEDES was readily soluble in various polyols (glycerin, 1,3-butylene glycol, dipropylene glycol, and 1,3-propanediol) at a high concentration (approximately 40%). Furthermore, compared to AA alone or the physical mixture of AA and Bet, AA-based THEDES significantly enhanced AA delivery through porcine skin. In an in vivo human study, THEDES-containing serum reduced the markers of aging and induced an even skin tone. These findings indicate the utility of AA and Bet-based THEDES as novel transdermal delivery systems for AA. Furthermore, our approach also showed good extension to developing gluconolactone, a well-known natural antioxidant, and Bet-based THEDES, showing potential application in transdermal delivery systems.
... Thus, the L-ascorbic acid concentration chosen for the Olea europaea oil was 8.0 wt.% with a ƞ value of 2.71 Pa.s (measured at a shear rate of 2.3 s −1 ) and E24 = 96% and 15 wt.% for Prunus amygdalus dulcis with a ƞ value of 5.15 Pa.s (at a shear rate of 2.3 s -1 ) and E24 = 99%. For cosmetic formulations containing ascorbic acid, the optimal concentration for a required effect must be higher than 5.0 wt.% [4,40], which was also a decision factor. ...
... Thus, the L-ascorbic acid concentration chosen for the Olea europaea oil was 8.0 wt.% with a η value of 2.71 Pa.s (measured at a shear rate of 2.3 s −1 ) and E24 = 96% and 15 wt.% for Prunus amygdalus dulcis with a η value of 5.15 Pa.s (at a shear rate of 2.3 s −1 ) and E24 = 99%. For cosmetic formulations containing ascorbic acid, the optimal concentration for a required effect must be higher than 5.0 wt.% [4,40], which was also a decision factor. ...
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The main function of vitamin C, as an antioxidant, is to combat free radicals and prevent premature aging, smoothing wrinkles and expression lines. In addition, it acts directly on depigmentation and prevention of blemishes on the skin. In this study, natural oils (30 wt.%) and α-tocopherol (2.5 wt.%) containing oil-in-water (O/W) emulsions stabilized with the bacterial fucose-rich polysaccharide FucoPol were formulated, adding L-ascorbic acid as an antioxidant. The optimized formulations were obtained with 8.0 wt.% L-ascorbic acid for the Olea europaea oil formulation (C1) with a ƞ value of 2.71 Pa.s (measured at shear rate of 2.3 s−1) and E24 = 96% and with 15 wt.% L-ascorbic acid for the Prunus amygdalus dulcis formulation (C2) with a ƞ value of 5.15 Pa.s (at a shear rate of 2.3 s−1) and E24 = 99%. The stability of the FucoPol-based formulations was investigated over 45 days at 4 °C, 20 °C, and 30 °C. The results showed that all formulations maintained the organoleptic characteristics, with pH variations (5.7–6.8 for C1, and 5.5–6.03 for C2) within the regulations for cosmetic products (4 ≤ pH ≤ 7). The accelerated stability tests proved the formulations’ stability at 4 °C with EI = 95% for C1 and EI = 100% for C2. The rheological assessment demonstrated that the formulation presents a shear-thinning and liquid-like behavior. Regarding textural parameters, formulations C1 and C2 displayed an increase in firmness and consistency with similar spreadability during the shelf life. These findings further demonstrate FucoPol’s functional properties, acting as an emulsifier and stabilizer polysaccharide in cosmetic formulations containing L-ascorbic acid.
... Photoprotective agents are divided into: (1) natural agents (occurring in nature, in the environment (ozone, clouds, fog, pollutants), and including the skin itself); (2) physical agents (clothes, hats, sunglasses), (3) sunscreens; and (4) antioxidants (found in the diet; they decrease the oxidative effects caused by exposure to ultraviolet radiation, such as vitamin E (tocopherol), vitamin C, beta-carotene, and flavonoids) [31][32][33]. ...
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Outdoor sports are associated with increased exposure to ultraviolet radiation, which may result in sunburn, solar damage, and skin cancers. Water and winter sports create additional adverse conditions, such as washing away sunscreen by water and reflection of UV rays by the water and snow. Sweating-increased skin photosensitivity and activity-induced immunosuppression are associated with a greater risk of developing skin cancers. In this review, we focus on a group of athletes and sports participants and analyze 62 articles concerning sun exposure during outdoor sports, the risk of developing skin cancer, and knowledge and behavior regarding photoprotection methods. Various practices have been linked to an increased risk of developing basal cell carcinoma (BCC), squamous cell carcinoma (SCC), malignant melanoma (MM), or UV-induced skin damage. Water sports and mountaineering increase the risk of BCC. Surfing and swimming are risk factors for SCC. Melanoma is more common in swimmers, surfers, and marathon runners. Photoprotection behaviors can reduce potential skin damage and skin cancers. Athletes’ knowledge about the risk of malignant lesions was satisfactory, but despite the risks, outdoor sports participants seem not to protect themselves from the sun adequately.
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Anti-aging creams have gained widespread popularity as a solution to combat the visible signs of aging, such as wrinkles, sagging, and uneven skin tone. These creams typically contain a variety of active ingredients designed to address different aspects of skin aging, including moisturizing, antioxidant effects, and promoting biological activity. Common ingredients found in anti-aging formulations include retinol, hyaluronic acid, peptides, and various plant extracts, each offering unique benefits in enhancing skin health. Retinol, for instance, is known for stimulating collagen production and improving skin texture, while hyaluronic acid helps retain moisture, reducing the appearance of fine lines. Furthermore, the use of antioxidants protects the skin from oxidative stress caused by free radicals, one of the primary contributors to premature aging. The effectiveness of anti-aging creams is determined through a range of evaluations, such as pH measurement, viscosity testing, spreadability, stickiness, and stability tests. These tests ensure that the product not only delivers the desired results but also remains safe and effective over time. Despite their popularity, the efficacy of these creams can vary depending on the formulation and the active ingredients used. This review explores the current understanding of anti-aging creams, their active components, and the methods used to assess their effectiveness, providing insights into their potential benefits and limitations
Chapter
Cosmeceuticals refer to a hybrid class of goods that fell between “cosmetics and pharmaceuticals. It exhibits a pharmaceutical therapeutic benefit. Antioxidants, peptides, vitamins, and other compounds are widely used cosmeceuticals that have been scientifically demonstrated to have positive benefits on the skin. The potent benefits of cosmeceuticals documented comprising Anti-aging, Skin hydration, Skin brightening, Acne treatment, Sun protection and Personal hygiene. Since the application and dosage of cosmeceuticals are personalized or precision-oriented, the dermatologist or skin care expert's approval is mandatory for accurate result. Mass increases in the manufacture and development of cosmeceuticals are reported worldwide. The modern era emphasizes external appearance and beauty, a prominent factor that has paved the way for success, self-esteem, confidence, and societal admiration. Both the physiological and psychological factors impact the rising demand on cosmeceuticals. Apart from the end result, the product's safety is vital in the mean process. The safety fundamentally relies on the source of origin, where biodiversity and nature are brought into the scenario. Compared to harsh chemical products, even though they acquire quick results within a very short time span, herbal/natural products are generally considered safe. Numerous cosmetic products are made from natural extracts or substances derived from microbes, plants, or animals. Also, the significant positive effects on the hair and skin health are also verified scientifically. Hence biodiversity could be considered a dependable source for the isolation, extraction and development of cosmetics in a genuine, trustworthy and safe manner. The integrity and authenticity of such products are much higher than those of synthetic items. Since humans have an instinct to explore and exploit nature, stringent laws and ethical perspective are extremely important while handling such sensitive cases. Ultimately the development of cosmeceuticals enhances the global market and business; bioprospecting should be implemented to prevent biological theft, injustice to indigenous people, loss of traditional knowledge, and unethical profit of multinational company. With a forecasted value of 380.2billionin2019andacompoundannualgrowthrate(CAGR)of5.3380.2 billion in 2019 and a compound annual growth rate (CAGR) of 5.3% from 2021 to 2027, the global cosmetics market is expected to reach 463.5 billion.
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Background Pregnancy striae, a common problem in pregnant women, create significant concerns about beauty in most women and there are challenges in preventing and treating them. The current research sought to investigate the impact of a vitamin “C + D” cream combination on striae distensae in primipara. Methods The current research was a clinical study with a control group, which was carried out in parallel with 60 primipara at 18–20 weeks gestational age, who presented at Shahid Akbarabadi Hospital in Tehran between 20/07/2022 to 20/01/2023. Sampling was done using a continuous method, and then allocated into two groups using a random block of 4 and 8 with the Sealed Envelope online software. One group received vitamin “C + D” cream (30 candidates) while the other group received a placebo cream (30 candidates). Both sets of candidates applied the creams to the skin of the abdomen, breasts, thighs, and hips twice daily for four months. Evaluation of the severity and quantity of stretch marks was performed with the Atwal’s numerical tool scale. An assessment was conducted by the investigator at the study center’s prenatal clinic before and at 4, 8, 12, and 16 weeks following the intervention. Results There were no notable disparities in individual and obstetrical characteristics between groups before the intervention (p > 0.05). Both the intervention and control groups did not have any striae before the intervention. After 4 weeks of intervention, no striae were observed in the combination cream group, while 50% of individuals in the control group had mild striae. After 8 weeks, no striae were observed in the combination cream group, while 50% of the control group had mild striae. After 12 weeks of intervention in the vitamin C and D group, only 16% of individuals had mild striae, while in the control group, 50% had mild striae and 16.67% had moderate striae. After 16 weeks of intervention, in the intervention group, 16% of individuals had mild striae, while in the control group, 50% had mild striae and 33.33% had moderate striae. There was a noticeable disparity in the development of pregnancy striae between the two groups at every point of observation. The vitamin C and D cream demonstrated efficacy in diminishing the appearance and intensity of striae in pregnancy, as well as impacting the timing of their appearance (p < 0.001). Conclusions Given the positive outcomes of utilizing combination of vitamin C and D to prevent pregnancy striae, along with its cost-effectiveness, safety, and reception among pregnant women, it is advisable for the prevention of striae during pregnancy. Clinical Trial Registration The study has been registered on https://trialsearch.who.int/ (registration number: IRCT20220509054799N1; the trial was registered on 06/06/2022).
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Ascorbic acid, as a one of the basic exogenous vitamins, occurs in the body in the form of ascorbate, known for its strong antioxidant and anti-inflammatory properties. The presented review shows not only the importance of ascorbate as a free radical scavenger but also summarizes its antioxidant action based on other mechanisms, including the activation of intracellular antioxidant systems and its effect on the NFκB/TNFα pathway and apoptosis. Ascorbate interacts with small-molecule antioxidants, including tocopherol, glutathione, and thioredoxin; it can also stimulate biosynthesis and the activation of antioxidant enzymes, such as superoxide dismutase, catalase, or glutathione peroxidase. Moreover, ascorbate promotes the activity of transcription factors (Nrf2, Ref-1, AP-1), which enables the expression of genes encoding antioxidant proteins. Additionally, it supports the action of other exogenous antioxidants, mainly polyphenols. In this regard, both DNA, proteins, and lipids are protected against oxidation, leading to an inflammatory reaction and even cell death. Although ascorbate has strong antioxidant properties, it can also have pro-oxidant effects in the presence of free transition metals. However, its role in the prevention of DNA mutation, inflammation, and cell apoptosis, especially in relation to cancer cells, is controversial.
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The pig has been a well accepted model for cutaneous absorption and toxicity studies because the integument is morphologically and functionally similar to human skin. We will review how the pig is utilized in this field, with particular reference to studies conducted in our laboratory. There has been considerable debate as to whether the topical effect of an antiinflammatory drug is due to direct penetration or is secondary to systemic absorption and recirculation. We addressed this question by studying the mechanism of topical penetration of piroxicam, a nonsteroidal antiinflammatory drug, in the pig. The pivotal role of the cutaneous vasculature on absorption will be further discussed and contrasted to in vitro systems. Pigs have been accepted as a model for studying iontophoretic drug delivery in humans. Transdermal delivery permits administration of therapeutic compounds that would not normally penetrate the skin. The pig is a principal animal model used in this field. The pathway a drug follows during delivery has been controversial and is of toxicological significance. We have defined the precise anatomical pathway which mercuric chloride traverses the stratum corneum during iontophoresis. In addition, new research methodologies have been applied in cutaneous toxicology, partly because of the driving force to replace in vivo animal models, with more humane in vitro approaches. The isolated perfused porcine skin flap (IPPSF), developed in our laboratory, is a perfused skin model which allows for in vitro cutaneous pharmacology and toxicology studies to be conducted in a viable system that has a morphological and functional microcirculation. A porcine skin model developed for use in phototoxicology will be characterized. Finally, studies involving use of this preparation to assess the toxicity of chemical vesicants will be discussed. These examples are illustrative of the dominant role of the pig as an animal model for human skin biology.
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L-ascorbic acid (ascorbate or vitamin C) is a required nutrient for humans. Absorption, transport, and disposition of ingested ascorbate involve the following: (1) bioavailability and absorption in the gastrointestinal tract; (2) presence in the circulation; (3) tissue distribution; (4) excretion; and, (5) metabolism. Fundamental to each of the above are ascorbate chemistry and mechanisms of transport of ascorbate across membranes. Ascorbate can be reversibly oxidized to dehydroascorbic acid, which can be irreversible degraded. Both reduced and oxidized forms cross cell membranes. Differences in transport kinetics, tissue specificity, and Na+ and energy dependence strongly support the existence of separate transport mechanisms. An important consideration in the analysis of ascorbate transport iss that of substrate availability. Reduced ascorbate is by far the most predominant form found in plasma and tissues. Dehydroascorbic acid is rapidly reduced intracellularly to ascorbate by both enzymatic and chemical mechanisms. Despite constitutively low levels of dehydroascorbic acid, conditions that promote oxidation of ascorbate can profound alter both the nature and availability of substrate. Elucidation of mechanisms that modulate the delivery of ascorbate to tissues and its utilization under different metabolic conditions will be invaluable for making recommendations for ascorbate ingestion. Published by Elsevier science Inc. 1998.
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In cancer chemoprevention studies, the identification of better anti- tumor-promoting agents is highly desired because they may have a wider applicability against the development of clinical cancers. Both epidemio- logical and animal studies have suggested that microchemicals present in the diet and several herbs and plants with diversified pharmacological properties are useful agents for the prevention of a wide variety of human cancers. Silymarin, a flavonoid isolated from milk thistle, is used clinically in Europe and Asia as an antihepatotoxic agent, largely due to its strong antioxidant activity. Because most antioxidants afford protection against tumor promotion, in this study, we assessed the protective effect of sily- marin on tumor promotion in the SENCAR mouse skin tumorigenesis model. Application of silymarin prior to each 12-O-tetradecanoylphorbol 13-acetate (TPA) application resulted in a highly significant protection against tumor promotion in 7,12-dimethylbenz(a)anthracene-initiated mouse skin. The protective effect of silymarin was evident in terms of reduction in tumor incidence (25, 40, and 75% protection, P < 0.001, X2 test), tumor multiplicity (76, 84, and 97% protection, P < 0.001, Wilcoxon rank sum test), and tumor volume (76, 94, and 96% protection, P < 0.001, Student's t test) at the doses of 3, 6, and 12 mg per application, respec- tively. To dissect out the stage specificity of silymarin against tumor promotion, we next assessed its effect against both stage I and stage II of tumor promotion. Application of silymarin prior to that of TPA in stage I or mezerein in stage II tumor promotion in dimethylbenz(a)anthracene- initiated SENCAR mouse skin resulted in an exceptionally high protective effect during stage I tumor promotion, showing 74% protection against tumor incidence (P < 0.001, X2 test), 92% protection against tumor multiplicity (P < 0.001, Wilcoxon rank sum test), and 96% protection against tumor volume (P < 0.001, Student's t test). With regard to stage II tumor promotion, silymarin showed 26, 63, and 54% protection in tumor incidence, multiplicity, and volume, respectively. Similar effect of silymarin to that in anti-stage I studies, were also observed when applied during both stage I and stage II protocols. In other studies, silymarin significantly inhibited: (a) TPA-induced skin edema, epidermal hyperpla- sia, and proliferating cell nuclear antigen-positive cells; ( b) DNA synthe- sis; and (c) epidermal lipid peroxidation, the early markers of TPA-caused changes that are associated with tumor promotion. Taken together, these results suggest that silymarin possesses exceptionally high protective ef- fects against tumor promotion, primarily targeted against stage I tumors, and that the mechanism of such effects may involve inhibition of promot- er-induced edema, hyperplasia, proliferation index, and oxidant state.
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The interaction between α-tocopherol and ascorbate in protecting membrane lipids from peroxidation was studied in unilamellar liposomes in which α-tocopherol was incorporated into the liposomal membrane, and ascorbate was trapped within the vesicles. Extravesi-cular ferricyanide was reduced by ascorbate-derived electrons, and this was enhanced by the presence of α-tocopherol in the lipid bilayer. When a water-soluble free radical initiator was added to the outside of liposomes, intravesicular ascorbate prevented oxidation of α-tocopherol, and this effect was associated with complete protection against peroxidation of membrane lipids. These results suggest that ascorbate-dependent recycling of α-tocopherol can protect biological membranes from peroxidation by oxidants originating across the membrane bilayer from ascorbate.
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We measured enzymic and non-enzymic antioxidants in human epidermis and dermis from six healthy volunteers undergoing surgical procedures. Epidermis was separated from dermis by currettage and antioxidants were measured by high-performance liquid chromatography (HPLC) or standard spectrophotometric methods. The concentration of every antioxidant (referenced to skin wet weight) was higher in the epidermis than in the dermis. Among the enzymic antioxidants, the activities of superoxide dismutase, glutathione peroxidase, and glutathione reductase were higher in the epidermis compared to the dermis by 126, 61 and 215%, respectively. Catalase activity in particular was much higher (720%) in the epidermis. Glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase, which provide reduced nicotinamide adenine dinucleotide phosphate (NADPH), also showed higher activity in the epidermis than the dermis by 111% and 313%, respectively. Among the lipophilic antioxidants, the concentration of α-tocopherol was higher in the epidermis than the dermis by 90%. The concentration of ubiquinol 10 was especially higher in the epidermis, by 900%. Among the hydrophilic antioxidants, concentrations of ascorbic acid and uric acid were also higher in the epidermis than in the dermis by 425 and 488%, respectively. Reduced glutathione and total glutathione were higher in the epidermis than in the dermis by 513 and 471%. Thus the antioxidant capacity of the human epidermis is far greater than that of dermis. As the epidermis composes the outermost 10% of the skin and acts as the initial barrier to oxidant assault, it is perhaps not surprising that it has higher levels of antioxidants.
Article
The improvement of the wound healing process in humans by vitamin supplements is still controversial because of the lack of a clearly demonstrated correlation with the mechanical properties of scars. Objective: The aim of this work was to study the effects of high doses of ascorbic acid (AA) and pantothenic acid (PA) on the wound healing process of human skin. Method: Two groups of patients undergoing surgery for tattoo removal by the successive resection procedure received AA (1 or 3 g/day) and PA (0.2 or 0.9 g/day). More than 80 mechanical, biological and histological parameters were investigated in both preoperated skin and the scars. Results: The breaking energy of scars was higher in group 2, and energy and treatment were directly correlated (p = 0.006). Mg and Mn significantly rose in group 2 whereas Fe decreased in a dose-dependent manner. Intragroup comparison showed patient and treatment effects for Mg, a time •treatment effect for Cu and a treatment effect for Fe. Conclusion: The degree and rapidity of variations rather than the variations of the absolute values themselves of fibroblasts, hydroxyproline, Fe, Cu and Mg are significantly related to the enhancement of the mechanical properties of scars. From this study, it may be assumed that in order to obtain ‘better’, more solid and resistant scars, the decrease of Fe must be quick and acute in order to avoid the harmful effects of toxic radicals; the increase of Cu, Mg and Mn must be early and high in order to have more stable and solid collagen.
Article
The reaction between ascorbic acid/ascorbate and molecular oxygen and its derivatives (HOâ/Oâ⁻) (AHâ/AH⁻) was followed from pH 0.3 to 11, leading to the following rate constants: kappaâ = 1.6 x 10⁴ M⁻¹ s⁻¹ for the reaction between AHâ and HOâ, kappaââ + 0.365 kappaââ = 1.22 x 10⁷ M⁻¹ s⁻¹ for the reactions between AH⁻ and HOâ and AHâ and Oâ⁻, respectively, and kappaââ = 5 x 10⁴ M⁻¹ s⁻¹ for the reaction between AH⁻ and Oâ⁻. The radical-radical reactions of A⁻ with HOâ and Oâ⁻ were measured and found to proceed at rates of kappaâ = 5 x 10⁹ s⁻¹ and kappaââ = 2.6 x 10⁸ M⁻¹ s⁻¹, respectively. An overall mechanism for the oxidation of AHâ/AH⁻ by HOâ/Oâ⁻ consistent with the experimental results is also proposed. 1 figure, 1 table.