Evaluation of antioxidant and anti-tyrosinase activities as well as stability of green and roasted coffee bean extracts from Coffea arabica and Coffea canephora grown in Thailand

Abstract

Coffea arabica (Arabica) and Coffea canephora (Robusta) are the economic plants in Thailand that are widely cultivated in Northern and Southern Thailand. This study aims to evaluate the antioxidant, anti-tyrosinase activities, toxicity, stability and identify chemical components of the coffee bean extracts. The best extract that showed good biological activities will be further used to develop cosmeceutical products. Green and roasted coffee beans from two species were extracted with hexane following ethanol by maceration. Their antioxidant activities were detected by 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2’-Azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and lipid peroxidation inhibition assays. In addition, anti-tyrosinase activity was also evaluated. The results revealed that the ethanolic coffee bean extracts showed a higher level of antioxidant activity than in the hexane extracts. All extracts also possessed a considerable anti-tyrosinase activity, but less potent than kojic acid and arbutin. Chemical compounds of these extracts were determined using caffeine and chlorogenic acid as standards of reference by the thin layer chromatography and the high performance liquid chromatography. The green coffee bean extracts consisted of caffeine and chlorogenic acid while the roasted coffee bean extracts presented only caffeine due to a few chlorogenic acid content after the roasting process. The ethanolic coffee bean extracts that showed good activities were selected to be evaluated on toxicity and stability. The selected extracts were kept at various storage conditions to evaluate their stability using DPPH assay and anti-tyrosinase activity assay. The result showed that the extracts were not toxic to cells. Therefore, the extracts were safe to be components in skin care products. After the stability test, the extracts indicated a good stability and activities. These results led to the conclusions that the coffee bean extracts possess a good biological activities and are assumed to be promising natural active ingredients with a good stability profile for further development of cosmeceutical or anti-aging products. Key words: Coffea arabica, Coffea canephora, green coffee bean, roasted coffee bean, antioxidant activity, anti-tyrosinase activity.