Development of nanostructure lipid carriers containing sticky rice husk extract for cosmetic applications

Abstract

There are numerous wastes, especially husk, from the rice production process of Oryza sativa var. glutinosa (glutinous rice), which is a famous and widely consumed in almost all parts of the country, particularly Northern and North-Eastern regions. As the rice husk had no value or limited further applications, this study aimed to increase the economic value of the rice husk waste by using in the cosmetic/cosmeceutical area. The present study aimed to enhance the extraction efficiency of glutinous rice husk by using aqueous enzymatic extraction (AEE) and incorporate the extract into nanostructure lipid carriers (NLCs) to enhance its stability and skin delivery. The rice husk was extracted by conventional solvent extraction using petroleum ther, ethyl acetate, and 95% v/v ethanol, as well as aqueous enzymatic extraction using 0.5, 1.0, and 1.5% w/w cellulose aqueous solution. The vanillic and ferulic acid contents of each extract were investigated by high-performance liquid chromatography. Their antioxidant and antiaging activities were investigated by spectrophotometric methods. The irritation effects of each extract were investigated by the hen’s egg test on chorioallantoic membrane. The glutinous rice husk extract, which possessed the highest biological activities and cause no irritation, was loaded into NLCs, which were developed using high-pressure homogenizer. Entrapment efficiency (EE%), release profile, skin permeation, and skin retention of the NLCs containing glutinous rice husk extract were determined. The results demonstrated that the rice husk extract from AEE using 0.5% w/w of cellulose (CE0.5) contained the significantly highest content of vanillic and ferulic acid (p<0.05), which were responsible for its biological activities, including the most potent antioxidant via radical scavenging activities (6.5 ± 0.3 mg Trolox/g extract), the most potent anti-skin wrinkle effect via collagenase and hyaluronidase activities with IC50 values of 0.4 ± 0.03 mg/mL and 47.5 ± 0.7 µg/mL, respectively (p<0.05). Aside from the superior biological activities, the rice husk extracts from AEE were safer than inorganic solvent extraction. The NLC, composing of 4% w/w sodium cocoyl hydrolyzed pea protein (Coco Pea.Soft®), 1% w/w cetyl alcohol, and 2% w/w rice bran oil, had the smallest internal droplet size (116.2 ± 0.7 nm), narrowest polydispersity index (0.2 ± 0.0), and suitable zeta potential (-40.7 ± 1.4 mV). It was found that NLC enhanced the physical and chemical stability of glutinous rice husk extract after 90 days. The entrapment efficacy of the extract in NLC was higher than 90%. The release amounts of vanillic and ferulic acid were 0.33 ± 0.01% w/w and 0.10 ± 0.01% w/w after 24 h, respectively. Besides, vanillic acid (0.013 ± 0.003% w/w) and ferulic acid (0.005 ± 0.001% w/w) were successfully delivered in to the skin with no skin permeation. In brief, the rice husk extracted by AEE had a potential to be used in the cosmetic/cosmeceutical area and NLC could enhance its stability and skin delivery.