Enhancement of Phenolics Content and Biological Activities of Longan (Dimocarpus Longan Lour.) Treated with Thermal and Aging Process

This study is the first to successfully produce novel black Dimocarpus longan by undergoing thermal and ageing process. Pericarp, aril, and seed of black D. longan were macerated in 95% v/v ethanol. Their chemical compositions were investigated by Folin–Ciocalteu assay, aluminium chloride assay, and high-performance liquid chromatography. Antioxidant activities were evaluated in terms of radical scavenging and iron (III) reducing capacity. Enzyme inhibitory assay was used to evaluate the hyaluronidase inhibition. Black D. longan seed extract contained the significantly highest content of flavonoids and phenolic compounds (p < 0.05). Each gram of the extract contained 53.6 ± 0.9 mg of gallic acid, 19.8 ± 2.9 mg of corilagin, and 24.5 ± 0.7 mg of ellagic acid. This extract was the most potent anti-hyaluronidase and antioxidant with the strongest free radical scavenging activity and reducing power. Therefore, it was proposed as functional food and further used in the pharmaceutical or cosmeceutical industries.