Kinetin (N6-furfuryladenine or 6-furfurylaminopurine) is a plant cytokinin or phytohormone that promotes cell division, delays senescence in plants, and is reputed to aid in the restoration of skin barrier function and, possibly, in reducing the signs and symptoms of rosacea (Clin. Exp. Dermatol. 2007;32:693-5; Plant Sci. 1999;148:37-45).
Kinetin is believed to develop in cellular DNA as a product of the oxidative, secondary modification of DNA (Plant Sci. 1999;148:37-45). In 1955, it became the first cytokinin isolated from DNA (from herring sperm) as an artifactual rearrangement product of the autoclaving process (J. Cosmet. Dermatol. 2007;6:243-9; Int. J. Biol. Macromol. 2007;40:182-92).
It has since been found to be present in human urine as well as DNA freshly extracted from human cells (Int. J. Biol. Macromol. 2007;40:182-92). The preponderance of amassed experimental evidence suggests that endogenous kinetin acts in vitro and in vivo as a potent antioxidant (Plant Sci. 1999;148:37-45). Currently, it is used as an anti-aging agent in various cosmetic products (J. Cosmet. Dermatol. 2007;6:243-9; J. Cosmet. Dermatol. 2010;9:218-25). Synthetic kinetin is thought to have the capacity to neutralize free radicals as well as limit the damage to DNA and fibroblasts (Photochem. Photobiol. 2012;88:748-52).
In vitro results
Olsen et al. demonstrated in vitro in 1999 that kinetin dose-dependently protected DNA against oxidative damage mediated by the Fenton reaction, and noted that kinetin had previously been linked to anti-aging activity in plants, fruit flies, and human cells in culture (Biochem. Biophys. Res. Commun. 1999;265:499-502). The following year, Verbeke et al. showed in vitro that kinetin potently inhibited damage caused by oxidation and glycoxidation (Biochem. Biophys. Res. Commun. 2000;276:1265-70).
In 2006, Vicanova et al. analyzed the effects of active ingredients from topical and systemic skin care formulations in vitro, finding that kinetin affected the upper dermis by enhancing deposits of fibrillin-1 and elastin fibers as well as their organization perpendicular to the dermal-epidermal junction. In the epidermis, kinetin stimulated keratinocyte production. Further, the investigators noted that the combination of topically applied kinetin with Imedeen Time Perfection ingredients (i.e., BioMarine Complex, grape seed extract, tomato extract, and vitamin C) supplemented systemically into culture medium yielded complementary benefits to dermal and epidermal development (Ann. N.Y. Acad. Sci. 2006;1067:337-42).
It is worth noting that in a study by Tournas et al. published the same month, investigators found that the topical application of a combination of vitamins C and E and ferulic acid yielded photoprotection to pig skin at 5 times the minimal erythema dose (MED) while individual antioxidants to which it was compared (i.e., coenzyme Q10, idebenone, and kinetin) delivered no photoprotective effects (J. Invest. Dermatol. 2006;126:1185-7). Nevertheless, Barciszewski et al. have observed that kinetin is the first stable secondary DNA damage product characterized by well defined cytokinin and anti-aging activity, with data showing that it has delayed human cellular aging in culture (Int. J. Biol. Macromol. 2007;40:182-92).
Rosacea
In 2007, Wu et al. performed a 12-week open-label study in 15 women and 3 men (aged 30-67 years) to ascertain the tolerability and efficacy of kinetin 0.1% lotion in the treatment of mild to moderate facial rosacea. Patients (17 of whom completed the study) applied the lotion twice daily, also daily applying an SPF 30 sunscreen. By week 4, significant improvements were observed in the reduction of skin roughness and mottled hyperpigmentation. Subject assessments at each 4-week interval after baseline and after 12 weeks revealed that kinetin 0.1% was well tolerated and effective for mild to moderate inflammatory rosacea (Clin. Exp. Dermatol. 2007;32:693-5).
Anti-aging
A 2002 study by J.L. McCullough and G.D. Weinstein represented the first evidence of the efficacy of topical kinetin in human beings, with twice-daily application for 24 weeks found to ameliorate skin texture, color, and blotchiness while diminishing rhytides and transepidermal water loss (J. Cosmet. Dermatol. 2002;15:29-32).
Two years later, T. Kimura and K. Doi showed that topical administration of kinetin improved the texture, wrinkling, and pigmentation of aged skin of hairless descendants of Mexican hairless dogs, resulting in notable depigmentation and rejuvenation after 100 days of treatment (Rejuvenation Res. 2004;7:32-9).In 2007, Chiu et al. conducted a randomized, double-blind, placebo-controlled, split-face comparative study in 52 Taiwanese subjects aged 30-60 years (90% of whom were female, all of whom had Fitzpatrick skin types II, III, or IV) to evaluate the clinical anti-aging effects and efficacy differences between kinetin plus niacinamide (kinetin 0.03%, niacinamide 4%) and niacinamide 4% alone versus vehicle placebo.
In the combination group, significant and sustained decreases were observed in counts of spots, pores, wrinkles, and evenness as well as persistent reductions in erythema index at weeks 8 and 12. At week 12, stratum corneum hydration status also was significantly enhanced in this group. In the niacinamide-only group, pore and evenness counts were significantly decreased at week 8, with declines in wrinkle counts emerging at week 12. The investigators concluded that kinetin and niacinamide display synergistic and dynamic anti-aging effects, showing substantial potential as topical anti-aging cosmeceutical agents (J. Cosmet. Dermatol. 2007;6:243-9).