Health Benefits and Safety of Red Pigmented Rice (Oryza sativa L.): In Vitro, Cellular, and In Vivo Activities for Hair Growth Promoting Treatment

Abstract

The hair growth-promoting activities of Thai native red (Sang-Yod-SY and Mun-Poo-MP) and black (Black glutinous-BG and Hom-Nil-HN) pigmented rice (Oryza sativa L.) extracts, including in vitro 5α-reductase inhibition, hair growth-promoting activity on human hair germinal matrix cells, and in vivo hair-cycle-converting activity in C3H/HeMlac mice, were investigated. Moreover, these extracts were determined to be safe via cytotoxicity (HaCaT cell) and in vivo irritation tests. The results showed that SY red rice extract with high contents of proanthocyanidin (1.50 ± 0.16 mgECE/g extract) exhibited significantly higher 5α-reductase inhibitory activity (18.5 ± 9.0 mgFEA/g extract) (p < 0.05). The maximum growth-promoting activity for human matrix cells treated with SY extract reached about 216.2 ± 0.7% (1 mg/mL) relative to control (100%) after 3 days culture (p < 0.05). Moreover, topical application of 1 mg/mL SY red pericarp rice extracts on shaven C3H skin in telogen phase led to significant hair regeneration (97.2 ±1.3%) based on the shaven area, while vehicle application only tended to yield a regeneration of 50.9 ± 11.7%. Red rice extracts were found to be safe, without signs of cytotoxicity and irritation. This research demonstrates the health benefits and safety of SY red pericarp extract when used for hair growing activity and its potential for use as a natural hair growth promoter and 5α-reductase inhibitor.