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Bakuchiol: a retinol-like functional compound revealed by gene
expression profiling and clinically proven to have anti-aging effects
R. K. Chaudhuri* and K. Bojanowski
†
*Sytheon Ltd., Boonton, NJ 07005, USA and
†
Sunny Biodiscovery, Santa Paula, CA 93060, USA
Received 04 November 2013, Accepted 25 January 2014
Keywords: anti-ageing clinical, bakuchiol, DNA microarray, histology, retinol
Synopsis
OBJECTIVE: The study was undertaken to compare the skin care
related activities of retinol and bakuchiol, a potential alternative to
retinoids. Retinol is a pivotal regulator of differentiation and
growth of developing as well as adult skin. Retinoic acid is the
major physiologically active metabolite of retinol regulating gene
expression through retinoic acid receptor –dependant and indepen-
dent pathways.
METHODS: Comparative gene expression profiling of both sub-
stances in the EpiDerm FT full thickness skin substitute model
was undertaken. Furthermore, type I, III and IV collagen, as well
as aquaporin 3 expression was analyzed by ELISA and/or histo-
chemistry in human dermal fibroblasts and/or Epiderm FT skin
substitutes.
RESULTS: Bakuchiol is a meroterpene phenol abundant in seeds
and leaves of the plant Psoralea corylifolia. We present evidence that
bakuchiol, having no structural resemblance to retinoids, can func-
tion as a functional analogue of retinol. Volcano plots showed
great overall similarity of retinol and bakuchiol effects on the gene
expression profile. This similarity was confirmed by the side-by-side
comparison of the modulation of individual genes, as well as on
the protein level by ELISA and histochemistry. Retinol-like func-
tionality was further confirmed for the upregulation of types I and
IV collagen in DNA microarray study and also show stimulation of
type III collagen in the mature fibroblast model. Bakuchiol was also
formulated into a finished skin care product and was tested in clini-
cal case study by twice-a-day facial application. The results showed
that, after 12 weeks treatment, significant improvement in lines
and wrinkles, pigmentation, elasticity, firmness and overall reduc-
tion in photo-damage was observed, without usual retinol therapy-
associated undesirable effects.
CONCLUSION: Based on these data, we propose that bakuchiol
can function as an anti-ageing compound through retinol-like
regulation of gene expression.
R
esum
e
OBJECTIF: L’
etude a
et
e men
ee pour comparer les activit
es li
ees
aux soins de la peau du r
etinol et du bakuchiol, une alternative
potentielle aux r
etino
€
ıdes. Le r
etinol est un r
egulateur essentiel de
la diff
erenciation et de la croissance de la peau en d
eveloppement
ainsi que la peau des adultes. L’acide r
etino
€
ıque est le principal
m
etabolite physiologiquement actif du r
etinol qui r
egule l’expres-
sion des g
enes par des voies d
ependantes et ind
ependantes du
r
ecepteur de l’acide r
etino€
ıque.
M
ETHODES: Un profilage comparatif d’expression g
en
etique de ces
deux substances dans le mod
ele substitut de la peau EpiDerm FT a
et
e entrepris. La synth
ese des collag
enes de type I, III et IV et de
l’aquaporine 3 dans des fibroblastes dermiques humains normaux
ont
et
e analys
es par ELISA et/ou en histochimie dans le mod
ele de
peau EpiDermTM FT.
R
ESULTATS: Bakuchiol est un ph
enol meroterp
ene abondant dans
les graines et les feuilles de la Psoralea corylifolia. Nous pr
esentons
des preuves que bakuchiol, n’ayant aucune ressemblance structu-
relle avec les r
etino
€
ıdes, peut fonctionner comme un analogue fonc-
tionnel de r
etinol. Les diagrammes de type Volcano montrent la
grande similitude de l’effet du r
etinol et du bakuchiol sur l’expres-
sion des g
enes. Cette ressemblance a
et
e aussi d
emontr
ee par la
comparaison de la modulation de l’expression de g
enes particu-
laires, appartenant a de diff
erentes groupes fonctionnelles. La fonc-
tionnalit
er
etinol -like a
et
e confirm
ee par la r
egulation
a la hausse
du collag
ene de type I et IV et aquaporine 3 au niveau de proteines
par ELISA et histochimie. Le bakuchiol a
egalement
et
e formul
e
dans un produit de soin de la peau et a
et
e test
e dans une
etude
clinique avec deux applications par jour au visage. Les r
esultats
ont montr
e que, apr
es le traitement de douze semaines, une
am
elioration significative a
et
e observ
ee dans les rides et ridules, la
pigmentation, l’
elasticit
e, la fermet
eetlar
eduction globale des
dommages du photo-vieillissement, sans les effets ind
esirables habi-
tuels associ
es
alath
erapie au r
etinol.
CONCLUSION: Sur la base de ces donn
ees, nous proposons que le
bakuchiol peut fonctionner comme un compos
e anti- vieillissement
gr^
ace
alar
eglementation de l’expression des g
enes similaire au
r
etinol.
Introduction
Retinoids have been first defined as a family of naturally occurring
compounds comprised of vitamin A (retinol) and its derivatives,
such as vitamin A aldehyde (retinal) or vitamin A acid (retinoic
acid). Retinoic acid is considered to be the active form of vitamin A
and is involved in gene regulation, leading to effects ranging from
hyperplasia to differentiation and apoptosis of normal and cancer
cells [1, 2]. The conversion of retinol to retinal by the retinol dehy-
drogenases is considered to be the rate-limiting step for the biosyn-
thesis of retinoic acid [3]. In addition to retinol dehydrogenases,
P450s 1A1, 1A2, 1B1 and 3A4 have been shown to be involved
Correspondence: Ratan K. Chaudhuri, Sytheon Ltd., 315 Wootton
Street, Boonton, NJ 07005, USA. Tel.: +201 303 5594; fax: +1 973
909 9922; e-mail: ratan@sytheonltd.com
©2014 Society of Cosmetic Scientists and the Soci
et
e Franc
ßaise de Cosm
etologie 1
International Journal of Cosmetic Science, 2014, 1–10 doi: 10.1111/ics.12117
in the metabolism of retinoic acid [4]. Human dermal fibroblasts
treated with retinol metabolize it to retinoic acid, demonstrating
the bioactivity and bioavailability of retinol in the dermis [5].
Retinol is found in a variety of foods such as beef, calf, chicken
liver, eggs and fish. It is also present in vegetables such as carrots,
squash, sweet potatoes, pumpkin and cantaloupe. Subsequent
research has resulted in a much larger class of natural and syn-
thetic compounds that are termed retinoids due to their functional
–although not always structural –similarity to vitamin A [6].
The epidermis is one of the major targets for the retinoic acid
signalling in adult organism. Classic retinoid activities are mainly
achieved through the transcriptional regulation of specific genes
via two classes of nuclear hormone receptors, the retinoic acid
receptors (RAR) and retinoid X receptors (RXR), each with three is-
otypes (a,b,c) and multiple isoforms [7–9]. All-trans retinoic acid
preferentially binds RARs and its 9-cis isomer, 9-cis retinoic acid,
binds both RARs and RXRs. The predominant retinoid receptors
found in skin are RARcand RXRa[10]. Retinoic acid receptors
exert their effects in epidermis through direct binding to epidermal
genes [11, 12] or interference with signalling of other transcription
factors [13].
Retinoic acid and its derivatives have been used as therapeutic
agents for numerous skin conditions from psoriasis to acne and
were also found to be clinically effective against wrinkles [14].
Retinol (Fig. 1A) application is believed to be a more efficient
method to deliver retinoic acid to the skin cells than direct treat-
ment with retinoic acid [15]. However, retinoid therapy using
even the newer analogues is still restricted by many undesirable
side effects, such as irritation, dryness, peeling, erythema and a
sensation of burning on the skin [16, 17]. These side effects often
result in non-compliance and discontinuation of therapy. There-
fore, there is a definite need to develop improved retinoid com-
pounds. Such compounds should have similar but not identical
gene expression pattern as compared with retinol, ideally, result-
ing in retinol-like beneficial effects, without having retinol-like
undesirable side effects. Here, we build on our preliminary findings
[18] and report that bakuchiol (Fig. 1B) –a meroterpene phenol
from seeds of the plant Psoralea corylifolia [19, 20] –exhibits such
retinol-like functionality.
Materials and methods
Test materials
Retinol (Fig. 1A), trade named Retinol 50 C (INCI name Retinol
and Polysorb 20), was purchased from BASF (Florham Park, NJ,
U.S.A). This product is a yellow oil containing 50% vitamin A in
polysorbate 20 and stabilizer system consisting of 3.5% BHT and
1% BHA. Bakuchiol (Phenol, 4-[1E,3S)-3-ethenyl-3,7-dimethyl-1,6-
octadinenyl; Fig. 1B)l is a phenolic compound with a monoterpene
side chain [19]. Bakuchiol belongs to a rare group of terpenoids in
which the aromatic ring system is derived from phenylpropane unit.
The material used in this study is obtained from edible seeds of Psora-
lea corylifolia, which is psoralene-depleted Bakuchiol (trade named Sy-
tenol
â
A; INCI name Bakuchiol) with a purity of about 95%.
DNA microarrays
EpiDerm FT tissues were obtained from Mattek (Ashland, MA,
U.S.A.; cat. no. EFT 212) and cultured according to the manu-
facturer’s instructions. The test materials –Retinol (50%) and
Bakuchiol (100%) were dissolved in DMSO at 10 mg mL
1
(Reti-
nol) and 5 mg mL
1
(Bakuchiol), and further dilutions were made
in type I sterile water. Test materials were assayed at 10 lgmL
1
(Retinol) and 5 lgmL
1
(Bakuchiol) against 0.1% DMSO as a con-
trol. The incubation time with skin tissues was 2 days. After incu-
bation, skin tissues were harvested, frozen in liquid nitrogen and
subjected to total RNA extraction with Qiagen kit (Frederick, MD,
U.S.A). The quality of extracted RNA was validated twice by elec-
trophoresis (after extraction and before microarray analysis).
Samples were hybridized and data were analysed using human
OneArray platform from Phalanx Biotech (Palo Alto, CA, U.S.A.).
The Excel file yielding information on over 30 000 probes was then
further processed in house to retain only differences with low P
values (Pvalue cut off was 0.05) and high fold-change (the cut off
value for fold-change was 2.0).
Collagen ELISA
Retinol and bakuchiol were assayed at 10 lgmL
1
on normal
human fibroblasts grown in DMEM with 5% calf serum (Hyclone,
Salt Lake City, UT, U.S.A.). For type I and IV collagen quantifica-
tion, neonatal human dermal fibroblasts (low passage; American
Type Culture Collection, Manassas, VA, U.S.A. cat. no. PCS-201-
010, lot no. 58243223) were used. For type III collagen quantifi-
cation, human epidermal fibroblasts from a 68-year-old female
donor (p. 5, Zen-bio, cat. no. KR-F) was used. Cells were exposed
to test materials for 3 days (type I collagen quantification) or
7 days (type III and IV collagen quantification). Afterward, cell-
culture conditioned media were harvested and assayed for type I,
type III or type IV collagen by sandwich ELISA using affinity-purified
antibodies, followed by streptavidin-avidin-HRP conjugate and ABTS,
according to a standard ELISA protocol [21, 22]. The colorimetric
signal proportional to collagen content was quantified with the Bio-
Rad microplate spectrophotometer 3550-UV at 405 nm with back-
ground subtraction at 660 nm and analysed with Microplate
Manager v.2 software for Macintosh (BioRad, Hercules, CA, U.S.A.).
Histochemistry
Fort type IV collagen and aquaporin three visualization retinol
and bakuchiol were dissolved at 50 mg mL
1
in DMSO. Test sam-
ples were then further diluted in type I sterile water and tested at
final concentrations 10 lgmL
1
(Retinol) and 5 lgmL
1
(Bak-
uchiol) using EpiDermFT tissues from Mattek. Tissues were equili-
brated for 24 h and incubated with test materials or water
(negative control) for 96 h, afterward they were rinsed and fixed
in 10% buffered formalin. Paraffin sections of these tissues were
stained with a biotinylated antibody against type IV collagen (cat.
B
A
HO
OH
Figure 1 (A) Retino l. (B) Bakuchiol.
2©2014 Society of Cosmetic Scientists and the Soci
et
e Franc
ßaise de Cosm
etologie
International Journal of Cosmetic Science, 1–10
A retinol-like functional compound R. K. Chaudhuri and K. Bojanowski
no. 1340-08 Southern Bio, Birmingham, AL, U.S.A.) or AQP3
(cat. no. sc-9885, Santa Cruz Biotechnology, Santa Cruz, CA,
U.S.A.) and developed with the ABC peroxidase staining compo-
nents (Santa Cruz Biotechnology). Slides were mounted in Perm-
mount and observed on Nikon (Tokyo, Japan) Eclipse TS100
inverted microscope at 100 magnifications. Microphotographs
were taken with Canon Rebel digital camera mounted on the
Nikon TS100 microscope.
Clinical study
General
Seventeen healthy but photo-aged subjects were recruited to this
blind study (all females; age range 40–65 years). All subjects read,
understood and signed an informed consent. All subjects had
abstained from the use of moisturizing products and used only sim-
ple soap, for at least 1 week prior to treatment conditions. All test
products were supplied in identical containers. Subjects were
instructed on the use of the cream –twice daily morning and even-
ing applications to the entire face for 3 months. Clinical assess-
ments of the skin of the face were performed for all participants at
baseline and following 4, 8 and 12 weeks of product use. The fol-
lowing parameters were assessed at each visit by an expert grader:
Fine Lines/Wrinkles, Roughness and Dryness, Skin Tone, Skin Elas-
ticity and Firmness, Radiance, Brightening and Overall Eye Area
Appearance. Assessment for each parameter was performed at
baseline using the following five-point ordinal severity scale:
0=None; 1 =Minimal; 2 =Mild; 3 =Moderate; 4 =Severe.
Silicone analysis profilometry
At each visit, a single silicone replica was made of the target area
and a photographic record was kept of this target for subsequent
relocation. Comparative analysis of skin profilometry was con-
ducted, using surface roughness and wrinkle depth analysis. The
heights of the replicated wrinkles were measured using Miyomoto
Surftest profilometer. Ry (depth) and Ra (mean roughness) were
recorded at each time of measuring operation. The area scanned
from each sample was clearly mapped so as to determine the same
area in respective weeks 4, 8 and 12 samples.
Photo booth
At each time point, a series of high resolution digital photographs
was collected using a photo booth equipped with Canon G7 Digital
Camera 10 MP, 69zoom. Subject positioning was reproduced
upon return visit. A light booth was used so as to provide con-
trolled reproducible light conditions. The booth consists of an array
of 8 equally spaced fluorescent tubes in a semicircular configura-
tion. The software-driven system allows the position and expression
of the test subjects to be aligned to a high degree.
Method of assessment & product application
Baseline
The expert grader performed assessment of the panelist’s face and
eye area for all the parameters as described before. Photographs
were conducted using a photo booth with a three-point head
restraint with photographs taken with frontal view, 45 degrees to
the right and 45 degrees to the left at each time point (Day 0,
Weeks 4, 8 and 12). A replica ring was used to delineate the wrin-
kle site in the crow’s feet area. Silflo was applied on the site,
allowed to dry for approximately 5 min, and the replica was
removed gently from the site.
Product application
Test Materials were distributed to the subjects. Subjects were asked to
gently massage a small amount of the test material to the crow’s feet
and eye area and then smooth over the whole face. They were asked
to apply twice a day for 12 weeks. A study diary was given to the
panelists to list the time of application, the dates and any subjective
comments that they might have in regard to the test product.
Weeks 4, 8 and 12
Panellists returned to the study site after week 4, 8 and 12 of prod-
uct use. At each study visit, panellists were clinically evaluated in
the same manner as at the baseline visit.
Statistical analysis
For each of the parameters, percent improvement from baseline
was calculated to express the efficacy of the product at each time
point (4, 8 and 12 weeks). Using the t-test, the statistical signifi-
cance of the net change from baseline (pre-application) to each
subsequent time point was assessed. Statistical significance was
defined at the P=0.05 or less level (corresponding to a 95% or
greater confidence level).
Formulated product
Formulation details are given in Table V.
Results and discussion
Bakuchiol is a meroterpene phenol abundant in seeds and leaves of
the plant Psoralea corylifolia [19, 20] and has also been isolated
from other plants, such as, P. grandulosa [23, 24], P. drupaceae
[25], Ulmus davidiana [26], Otholobium pubescens [27] and Piper lon-
gum [28]. It is widely used in Indian as well as Chinese medicine to
treat a variety of diseases. Bakuchiol has been reported to possess
anti-inflammatory [24, 29–31], antioxidant [32–34], anti-tumor
[35, 36], anti-bacterial [37], cytotoxic [38], heptaprotective [39]
and caspase-3 depended apoptosis [40] effects. The cytotoxicity of
bakuchiol is mainly due to its DNA polymerase 1-inhibiting activity
[41]. Recently, anti-acne activity of bakuchiol has been reported
[42]. Here, we demonstrate the anti-ageing and retinol-like func-
tionalities of bakuchiol using DNA microarray, ELISA, histochemis-
try and clinical case studies.
As human skin naturally ages, it becomes thin, lax and finely
wrinkled. Of these changes, fine lines & wrinkles and uneven pig-
mentation are most easily appreciated clinically with severity corre-
lating strongly with age. We have demonstrated through a pilot
clinical study that topical 0.5% bakuchiol treatment improves clini-
cal appearance (% improvement vs. baseline) of naturally aged/
photo-aged human skin.
DNA microarrays
As retinol affects the expression of a vast array of genes, compara-
tive gene expression profiling with retinol is a suitable method to
identify retinol-like compounds [43]. Here, we applied this method
©2014 Society of Cosmetic Scientists and the Soci
et
e Franc
ßaise de Cosm
etologie 3
International Journal of Cosmetic Science, 1–10
A retinol-like functional compound R. K. Chaudhuri and K. Bojanowski
to reveal retinol-like properties of bakuchiol. These proprieties were
first evidenced on the whole genome scale by comparing the shapes
of volcano plots of retinol- and bakuchiol-treated skin substitutes
(Fig. 2A,B). Volcano plot is a scatter graph used to identify mean-
ingful changes in large datasets, such as data from DNA micro-
array analysis, by plotting significance versus. fold-change on the
y- and x-axes, respectively. Data points with low P-values (highly
significant) appear towards the top of the plot, and with Pvalue of
0.05 being set as the threshold for statistical significance, all points
situated above the value of 1.3 on the y axis are statistically signifi-
cant. The finding that the overall shapes of retinol and bakuchiol
volcano plots are similar was the first indication of the functional
analogy between the two compounds. This was further confirmed
by the analysis of retinoid-binding and metabolizing genes; the
expression was often –but not always –similarly modulated
(Table I). Interestingly, both RARB and RARG are up-regulated, as
expected, by retinol but not by bakuchiol, indicating a possible
advantage of the latter in terms of side effects. Also retinol had no
effects on CRBP II and CRBP IV, whereas bakuchiol showed signifi-
cantly higher up-regulation. Furthermore, retinol causes down reg-
ulation of CRABP1 gene whereas bakuchiol causes up-regulation,
and whereas bakuchiol showed a dramatic up-regulation (82-fold
vs. placebo) of LRAT retinol showed 12.3-fold (still a very signifi-
cant) increase. These results indicate that besides being a retinol
functional analogue, bakuchiol may enhance the availability of
endogenous retinol.
Retinol and bakuchiol also showed similar modulation of genes
implicated in ECM and DEJ (Tables II and III, respectively). ECM is
the material that forms the bulk of the dermis, excluding water and
cells. Proteins and complex sugars form most of the dermal ECM, and
they are arranged in an orderly network fibres and ground sub-
stances organized by physical entanglements, opposing ionic
charges, chemical covalent bonding and cross-linking into a
biomechanically active polymer. This scaffolding structure with
regional tensile strength provided by collagens, elasticity by elastins,
Table I Description, fold-change in the DNA microarray experiment and role of modulated retinoid binding and metabolizing genes (R: retinol; B: bakuchiol)
Gene Full name Function & comments
CRBP I;
CRBP II;
CRBP IV
Cellular retinol binding
protein I, II & IV
CRBP I:R =2.6; B =4.2
CRBP II: R =NS; B =4.1
CRBP IV: R =NS; B =3.1
CRBP I mediates the cellular uptake of retinol, solubilizes and detoxifies it for further transport within the
cytoplasm and presents it to the appropriate enzymes to biosynthesize retinoic acid
N6AMT2 N-6 adenine-specific
DNA methyltransferase 2
R=NS; B =2.1
Retinoic acid resistance might be overcome by the use of epigenetic modifying agents such as DNA methyl
transferase inhibitors. Down-regulation provided by bakuchiol may reduce retinoic acid-induced toxicity
TIG1 Tazarotene-inducible gene 1 R =13.2; B =12.9
Retinoid acid (RA) receptor-responsive gene. The expression of this gene is found to be down-regulated in a
variety of human cancers as well as in acne, rosacea and psoriasis. Up-regulation by bakuchiol may provide a
solution to problem skin. Anti-acne clinical study results of bakuchiol has recently been reported [40]
DHRS9 Dehydrogenase/reductase
SDR family member
9 precursor
R=5.5; B =11.6
DHRS9 is involved in converting retinol to retinal and then to retinoic acid, the rate-limiting step for the
biosynthesis of retinoic acid
RETSAT All-trans- 13,14-dihydroretinol
saturase
R=2.9; B =2.8
RETSAT expression is involved in adipocyte differentiation
LRAT Lecithin-retinol acyltransferase R =12.3; B =82.2
Retinol esterification with long-chain fatty acid by LRAT is the key step in both absorption & storage of retinol.
CYP1A1;
CYP1A2
Cytochrome P450 CYP1A1: R =4.0; B =4.9
CYP1A2: R =3.6; B =6.7
In addition to retinol dehydrogenase, P450s 1A1 and 1A2 genes are the major human P450s
RARB; RARG Retinoic acid receptor beta -1;
Retinoic acid receptor
gamma -1
RARB: R =5.6; B =NS
RARG: R =1.8; B =NS
The actions of retinoids are generally mediated by the retinoic acid receptors (RARs alpha, beta, and gamma) and
the retinoid X receptors (RXRs alpha, beta, and gamma). Both RARB and RARG are up-regulated, as expected
by retinol but not with bakuchiol
0
2
4
6
–3 –2 –1 0 1 2 3
–Log (P value)
Log2 (fold change)
Retinol
0
2
4
6
–3 –2 –1 0 1 2 3
–Log (P value)
Log2 (fold change)
Bakuchiol
A
B
Figure 2 (A) Volcan ic plot of DNA microarray data –Retinol. (B) Volcanic
plot of DNA microarray data –Bakuchiol.
4©2014 Society of Cosmetic Scientists and the Soci
et
e Franc
ßaise de Cosm
etologie
International Journal of Cosmetic Science, 1–10
A retinol-like functional compound R. K. Chaudhuri and K. Bojanowski
adhesiveness by structural glycoproteins, compressibility by proteo-
glycans –hyaluronans and communicability by transmembrane
receptors, such as integrins, which exchange information between
the cytoskeleton-bound cellular elements and between cells and the
dermal extracellular matrix, provides a unique homeostatic tenseg-
rity function to the skin [44, 45]. DEJ, in turn, provides cohesion
between dermis and epidermis. With age, both, ECM and DEJ
gradually deteriorate resulting in skin thinning and morphological
Table II Description, fold-change in the DNA microarray experiment and roles of modulated genes coding for ECM components [(R: retinol; B: bakuchiol]
Gene Full name Function & comments
COL1A2;
COL4A6;
COL9A2;
COL9A3;
Collagen 1A2;
Collagen 4A6;
Collagen 9A2;
Collagen 9A3
COL1A2: R =3.3; B =1.9
COL4A6: R =6.4; B =11.2
COL9A2: R =5.6; B =6.7
COL9A3: R =4.1; B =5.8
Collagens provide scaffolding structure with regional tensile strength and elasticity; Degradation leads to fine lines and
wrinkles. Comparable fold-change observed with four collagen genes with the exception of COL3A1. This may be due
to the use of neonatal tissue in the skin substitutes. ELISA study with mature fibroblasts showed stimulation of type III
collagen.
EMILIN3
EMILIN1
Elastin microfibril
interface-located protein 3;
Elastin microfifibril
interface-located protein 1
EMILIN3:R =2.2 (NS); B =9.1
EMILIN1: R =3.4; B =2.4
The EMILINs are a family of glycoproteins of the extracellular matrix; Widely distributed in several tissues associated
with elastin and localized at the interface between amorphous elastin and microfibrils
PI3 Peptidase inhibitor
3/Elastase-specific inhibitor
R=2.5; B =2.7
Bakuchiol and retinol are expected to maintain the desired level of elastin required for maintaining the connective
tissue structure due to their up-regulation of elastase-specific inhibitor gene PI3
FLRT2;
FLRT3
Fibronectin-like
domain-containing
leucine-rich transmembrane
protein 2
FLRT2: R =NS; B =13.9
FLRT3: R =2.8 (NS); B =6.1
Fibronectins maintain the shape of cells and matrix stability
HAS3 Hyaluronan synthase 3 R =10.8; B =19.2
Hyaluronans are important for the maintenance of a highly hydrated extracellular matrix in tissues and is also involved
in cell adhesion and supports cell migration. It is synthesized by hyaluronan synthases, such as HAS-3
AQP3 Aquaporin 3 R =3.5; B =4.3
Aquaporin 3 is the water/glycerol transporting channel protein expressed in the epidermis which helps maintain the
right level of skin hydration, elasticity and barrier recovery. Both retinol and bakuchiol up-regulated AQP3
Table III Description, fold-change in the DNA microarray experiment and roles of modulated DEJ genes (R: retinol; B: bakuchiol)
Gene Full name Fold-change, function & comments
COL4A6
COL17A1
Collage alpha-6 (IV)
Collagen alpha-1(XVII)
COL4A6: R =6.4; B =11.2
COL17A1: R =3.6; B =8.7
Lamina densa mostly consists of type IV collagen, perlecan and nidogen. Through a complex inter- and intramolecular
interactions type IV collagen forms supra molecular networks that influence cell adhesion, migration, and
differentiation. Type XVII collagen is the protein component of anchoring fibrils that fortifies the attachment of the
epidermis to the dermis.
PLEC1 or
HD1
Plectin I
(Hemidesmosomal
protein 1)
R=2.7; B =6.8
Plectin, a 500-KDa protein and a constituent of the intracellular component of hemidesmosomes, attaches intermediate
filaments to both hemidesmosomes and plasma membranes of basal keratocytes
ITGB4;
ITGB6;
ITGB8;
ITGA6
Integrin beta-4;
Integrin beta-6;
Integrin beta-8;
Integrin alpha-6
ITGB4: R =3.5; B =8.0; ITGB6: R =7.5; B =7.7
ITGB8: R =0; B =3.9; ITGA6: R =0; B =3.6
Integrins are transmembrane glycoproteins and a major component of hemidesmosomes. They mediate the transfer of
information between the extracellular matrix and the interior of the cell, thereby aiding in modulating the organization of
the cytoskeleton, proliferation and differentiation. Main functions: (a) attachment of the cell to the ECM and (b) signal
transduction from ECM to the cell
LAMA3;
LAMC2
Laminin subunit alpha-3
precursor; Laminin
subunit gamma-2
precursor
LAMA3: R =4.7; B =11.0;
LAMC2: R =2.7; B =7.8
Laminins are the major non-collagenous proteins in lamina densa and are integral part of the structural scaffolding in
almost every tissue; Involved in cell differentiation, migration, adhesion as well as phenotype and survival.
CDH1 E-Cadherin R =9.4; B =21.6
One of the most important and ubiquitous types of adhesive interactions required for the maintenance of solid tissues
is that mediated by E-cadherin. E-cadherin has important functions in pluripotency and maintenance of the
differentiated state of cells
©2014 Society of Cosmetic Scientists and the Soci
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A retinol-like functional compound R. K. Chaudhuri and K. Bojanowski
flattening [46]. Retinol is a well known inhibitor of those processes,
and the finding that bakuchiol has retinol-like functionality at the
ECM and DEJ levels makes it an interesting novel candidate for
anti-ageing applications.
Validation of DNA microarray results by ELISA and histochemistry
Collagens secreted by dermal fibroblasts are major components of
the skin extracellular matrix (type I and type III collagens) and
basement membrane (type IV collagen). In aged and photodamaged
skin, the new collagen pool is decreased due to the inferior amount
and quality of dermal fibroblasts. Therefore, we chose to measure
select collagens by ELISA and histochemistry methods to validate
the data obtained by DNA microarrays. The results, summarized in
the Table IV, confirm the upregulation of types I and IV collagen
in DNA microarray study and also show stimulation of type III
collagen in this mature fibroblast model.
To determine whether the stimulation of type IV collagens in cell
culture translates into a more robust collagen expression in 3D
skin substitute tissue, EpiDermFT tissues were incubated with bak-
uchiol or retinol at 10 lgmL
1
, and histological sections were
stained with anti-type IV collagen antibodies (Fig. 3). The stain
revealed a stronger type IV collagen signal at the dermal–epidermal
junction, as compared with the water control, further corroborat-
ing the DNA microarray and ELISA results. This collagen stimula-
tory effect observed in cell culture seems to be due to the selective
metabolic activation of collagen synthesis in fibroblasts, because at
10 lg/mL
1
, bakuchiol or retinol did not enhance cell proliferation
(results not shown).
Water homeostasis of the epidermis is essential for the normal
function of the skin and stratum corneum (SC) hydration. It is a
determinant of skin appearance, mechanical properties, barrier
function and metabolism. In addition, it is indispensable in main-
taining proper water balance of the body. Dehydration of SC is a
typical feature of skin ageing, especially in photo-aged skin and of
Table IV Comparative collagen stimulatory effects of bakuchiol and retinol
as determined by ELISA in human dermal fibroblasts. The stimulatory effect
is expressed as the % of water control (100%)
Test material (10 lgmL
1
) Collagen I Collagen III Collagen IV
Bakuchiol 147 150 119
Retinol 119 148 100
ABC
Figure 3 Effect of Retinol (B) and Bakuchiol (C) on type IV collagen expression compared with non-treat ed control (A) in human EpidermFT (full thickness)
tissue substitutes. Arrows indicate dermo-epidermal juncture (basement membrane), where collagen IV is localized. Note darker band in (B) and (C) as com-
pared to (A) at this level, indicating greater type IV collagen expression.
AC
B
Figure 4 Effect of Retinol (B) and Bakuchiol (C) on aquaporin-3 expression, compared with non-treated control (A) in human EpidermFT (full thickness) tissue
substitutes. Arrows indicate aquaporin-3 staining in the basal layer, where this protein is principally localized.
6©2014 Society of Cosmetic Scientists and the Soci
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International Journal of Cosmetic Science, 1–10
A retinol-like functional compound R. K. Chaudhuri and K. Bojanowski
several diseases, for example, eczema, atopic dermatitis, psoriasis
and hereditary ichthyosis (retinol 3.5 fold and bakuchiol 4.3 fold,
Table II) [47–50]. To determine whether the increase of the !!!
expression of water channel AQP3 gene observed in DNA micro-
arrays translates into orthotropic increase at the protein level.
EpiDermFT skin substitutes were incubated with retinol, bakuchiol
and compared with the negative (water) control using immunohis-
tochemistry. It was found that both retinol and bakuchiol increased
AQP3 expression (Fig. 4) as visualized by more intense brown col-
oration in retinol and bakuchiol –treated tissues located, as
expected, at stratum spinosum and corneum level. Recently, Belle-
mere et al. [51] have shown the effects of all-trans retinoic acid
(ATRA) on AQP3 expression and function both in vitro and ex
vivo. ATRA treatment increased a rapid accumulation of AQP3
transcripts in cultured normal human epidermal keratinocytes.
Also in our model of EpiDermFT skin substitute, both retinol and
bakuchiol increased AQP3 expression.
Clinical study
Taken together, these results prompted us to test bakuchiol clinically.
The formulated product containing 0.5% bakuchiol (no moisturizer
or any other active ingredients or sunscreen included in this formu-
lated product; Table V) was applied twice daily to the whole face.
Sixteen subjects of seventeen enrolled completed the study. One sub-
ject discontinued due to protocol violation. Each of the parameters
was graded on a semi-quantitative scale from 0 to 4 (0, none; 1,
minimal; 2, mild; 3, moderate; and 4, severe). With regard to subjec-
tive evaluation by experts and panelists, the obtained results for the
entire subjects are summarized in Tables VI and VII, respectively.
Evaluations were performed at baseline and then at 4, 8 and
12 weeks and the results compared versus. the baseline.
Retinol is used widely in cosmetic products for reducing the
appearance of the signs of ageing and photo-damage [52]. Retinol
is a precursor of retinoic acid. Once it penetrates skin, it is sequen-
tially oxidized to retinoic acid, causing retinoic acid-like effects, but
is notably less irritating. Currently, most of these products contain
0.1% or lower of retinol. However, even at this low concentration,
some irritation can occur [53]. It seems that bakuchiol has accept-
able skin tolerability.
Analysing the data (Table VI vs. Table VII), it is evident that %
improvement score for roughness & dryness and radiance given by
expert is significantly higher versus. the panelists’ self-evaluation. It
is interesting to note that % improvement score given by the sub-
jects, on the other hand, for fine lines and wrinkles and eye area
appearance is significantly higher than the score given by the
expert. Most of the parameters were improved significantly more
after 8 weeks compared to 4 weeks of application of bakuchiol,
showing a certain degree of cumulative beneficial effect over time.
Results obtained from silicone replica analysis using profilometry
are summarized in Table VIII. Comparison of results of day 0 (base
line) vs. 4, 8 and 12 weeks treated skin provided 7%, 13% and
20% reduction in wrinkle depth (Ry), respectively. All three
results are statistically significant (P≤0.01). Comparison of results
of day 0 (baseline) versus. 4, 8 and 12 weeks treated skin yielded
Table V Formulation details of bakuchiol
Ingredient Trade name/supplier % w/w
Phase A
Glyceryl stearate
and PEG-100
Arlacel 165/Uniqema 1.50
Arachidyl alcohol,
Behenyl alcohol,
Arachidyl glucoside
Montanov 202/Seppic 4.00
Dimethyl isosorbide Arlasolve DMI/Uniqema 3.00
Isohexadecane Permethyl 101A/Presperse 8.00
Dimethicone Dow Corning 200, 100 cst/Dow Corning 2.00
Bakuchiol Sytenol A/Sytheon 0.50
Phase B
Water 69.75
Propylene Glycol Propylene glycol/Lyondell 2.00
Pentylene Glycol Hydrolite-5/Symrise 3.00
Xanthan Gum Vanzan NF/Vanderbilt 0.25
Phase C
Dicaprylylether Cetiol OE/Cognis 4.00
Hydroxyethylacrylate
(and) sodium
acryloyldimethyl
taurate copolymer
Sepinove EMT 10/Seppic 1.00
Phenoxyethanol
(and) Caprylyl glycol
Optiphen or Microcare PHG 1.00
Total 100.00
Table VI Subjective evaluation by expert –% improvement vs. baseline
Parameters 4 Weeks 8 Weeks 12 Weeks
Roughness & dryness 65 81 90
Fine lines/wrinkles 5 16 29
Skin tone 14 29 39
Skin elasticity/firmness 13 20 39
Radiance 24 40 52
Skin brightening 13 35 46
Eye area appearance 8 24 46
Table VII Subjective evaluation by panelists –% improvement vs. baseline
Parameters 4 Weeks 8 Weeks 12 Weeks
Roughness & dryness 35 40 48
Fine lines/wrinkles 19 25 23
Skin tone 12 19 29
Skin elasticity/firmness 14 23 25
Radiance 11 17 30
Skin brightening 10 14 29
Eye area appearance 22 24 35
Table VIII Silicone replica analysis using profilometry: % reduction vs.
baseline
Parameters 4 Weeks 8 Weeks 12 Weeks
Wrinkle depth 7% 13% 20%
Skin roughness 2% 10% 21%
©2014 Society of Cosmetic Scientists and the Soci
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ßaise de Cosm
etologie 7
International Journal of Cosmetic Science, 1–10
A retinol-like functional compound R. K. Chaudhuri and K. Bojanowski
2%, 10% and 21% reduction in skin roughness (Ra), respec-
tively. The results at 8 and 12 weeks are statistically significant
(P≤0.004).
The photos (Fig. 5; before and after treatment) shown here are
representative of the results that have been obtained with bakuchi-
ol treatment for 12 weeks.
Clinical grading and comparative analysis of skin profilometric
measurements were performed at baseline and after 4, 8 and
12 weeks of application. After 8 weeks of daily application, a
significant reduction in the wrinkle depth and roughness was
observed with the product vs. baseline. These changes were even
greater after 12 weeks of product application. For example, wrinkle
depth reduction (Fig. 5C) is significantly more after 8 weeks com-
pared to 4 weeks of application of bakuchiol (subject no. M572)
showing a certain degree of cumulative beneficial effect over time.
The significant improvement in fine lines and wrinkles, elasticity,
firmness and overall reduction in signs of photodamage including
even toning effects observed after 12 weeks of treatment provided
the ultimate validation of the in vitro results and were in line with
the retinoid-type functionality of bakuchiol.
Conclusion
Given the fact that retinol and bakuchiol do not have close struc-
tural similarities, yet they exhibit a similar gene expression profile,
especially on certain key anti-ageing genes and proteins,which is
remarkable. Bakuchiol has several substantial advantages over reti-
nol, including excellent photochemical and hydrolytic stability a
good safety profile and ease to formulate due to miscibility with a
wide variety of emollients and solubilizers [18]. Bakuchiol can be
used during the day due its photostability. Interestingly, bakuchiol
is an excellent stabilizer of retinol under photo-oxidative as well as
singlet oxygen environments (not discussed here). This property
may help reduce oxidative stress caused by retinol when combined
with bakuchiol and used at concentrations higher than the physio-
logical limit [54].
This open clinical pilot study needs further confirmation of bak-
uchiol bioactivity in vivo, from vehicle- or benchmark-controlled
studies. The similarity of gene expression and protein synthesis
stimulation observed in the comparison of bakuchiol with retinol
is, however, remarkable and suggests that similar bioactivity in vivo
is probable. Taken together, this study demonstrates the potential
of bakuchiol, a true retinol-like functional compound, to become a
key ingredient for dermatological and skin care products.
Acknowledgements
The authors would like to thank Sytheon Ltd for funding this
research and to Stephanie Ma for her dedicated assistance in this
project.
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