Application of Hibiscus cannabinus L. (kenaf) leaves extract as skin whitening and anti-aging agents in natural cosmetic prototype

In Malaysia, the industrial wastes from the Hibiscus cannabinus L. (kenaf) industry, especially leaves, cause challenges in sustainability. The biological activity of kenaf leaves was reported by few previous studies, it is therefore believable that the kenaf leaves extract (KLE) can be used as functional ingredient in cosmetic formulations. Thus, the aim of this study was to develop a natural cosmetic formulation containing KLE and evaluate it physicochemical characteristics, microbiological properties, storage stability, biological activities (antioxidant, antityrosinase, and anti-aging), in vitro cytotoxicity (on normal human dermal fibroblast and B16F10 melanoma cells) and melanogenesis assay (intracellular tyrosinase activity and reduction of melanin production). The results showed that KLE lotion (KLEL) prepared by 15 % kenaf seed oil (KSO) (F2) with 0.1 % w/w KLE yields the best physical and microbiological stability, with no toxicity on human cells. The KLEL also presented antioxidant content up to 1.84 ± 0.07 mg caffeic acid equivalent (CAE)/g and 21.62 ± 0.76 mg catechin hydrate equivalent (CHE)/g for total phenolic content (TPC) and total flavonoid content (TFC), respectively. In addition, the KLEL presented antityrosinase capacity on inhibition of monophenolase (30.28 ± 3.90 %) and diphenolase (11.40 ± 0.29 %) formation, and revealed, for the first time, anti-aging properties by inhibiting collagenase (36.41 ± 0.54 %) and elastase (23.13 ± 1.56 %) activities. Concerning on melanogenesis inhibitory activity, KLEL presented high efficacy in suppressing cellular tyrosinase activity and melanin content on B16F10 cells. Overall, the results from this study are very promising towards the development of natural cosmetic prototypes using kenaf leaves.