Early this year, Dhaliwal et al. reported on a randomized, double-blind, 12-week study of 44 patients who applied either bakuchiol 0.5% cream twice daily or retinol 0.5% cream daily. Facial photographs were evaluated at baseline, 4, 8, and 12 weeks, and a blinded dermatologist rated pigmentation and erythema. Side effects were also noted by subjects in tolerability assessment questionnaires. Both compounds significantly reduced wrinkles and hyperpigmentation, with no statistical variance found between the two. More facial skin scaling and stinging was experienced by the retinol group. The investigators concluded that bakuchiol exhibits photoaging activity comparable with retinol and appears to be an emerging alternative to retinol because it is better tolerated.12 Notably, there is one report to date of an allergic reaction to topical bakuchiol.15
Topical combination therapies for hyperpigmentation, photodamage, and acne
Bakuchiol was a key ingredient incorporated into a 0.5% retinol treatment evaluated in a 12-week, open-label, single-center clinical-usage trial of 44 women with mild to moderate hyperpigmentation and photodamaged facial skin who took a dual product regimen. This 2016 study showed that the retinol and vitamin C facial regimen yielded a statistically significant amelioration in clinical grading of all parameters.16
A 2015 randomized controlled clinical trial in 111 subjects evaluated the use of adapalene 0.1% gel and a formulation containing bakuchiol, Ginkgo biloba extract, and mannitol in patients with acne. Patients were randomized to the adapalene and botanical formulation or adapalene and vehicle cream for 2 months. Both treatment groups experienced improvements according to all measured outcomes. The botanical formulation was associated with a statistically significant edge over the vehicle combination in reducing inflammatory lesions, investigator global assessment, and intensity of seborrhea. Quality of life was also perceived to be better with the combination of adapalene and the bakuchiol-containing product, which was deemed to be safe with good local tolerability.17
A subsequent evaluation by a different team also considered the antibacterial, anti-inflammatory, and antioxidative potential of this combination product via in vitro, ex vivo, and clinical studies. The work by Trompezinski et al. revealed that bakuchiol displays nearly twice the antioxidative potential asthat of vitamin E. The bakuchiol-containing cream was shown in acne patients to successfully regulate sebum composition by raising linolenic and sapienic acid levels while lowering oleic acid levels. Its efficacy against Propionibacterium acnes was also suggested by a decrease in the number of skin surface porphyrins. The investigators concluded that the formulation serves as an effective adjuvant acne treatment by attacking inflammation, dysseborrhea, and proliferation of Propionibacterium acnes.18
Anticancer activity
In 2016, Kim et al. demonstrated that bakuchiol exhibits chemopreventive activity by hindering epidermal growth factor (EGF)–induced neoplastic cell transformation. In what was the first mechanistic study to reveal molecular targets for the anticancer activity of this substance, the investigators found that bakuchiol also reduced the viability and suppressed anchorage-independent growth of A431 human epithelial carcinoma cells. They identified Hck, Blk, and p38 MAPK as the molecular targets of what they identified as a potent anticancer compound.2