Safety, Nutritional Value and Biological Activities of Guava (Psidium guajava) Seed Oil Extract

Abstract

Guava (Psidium guajava Linn. var Pan See Tong strain) is an edible fruit and important in the food industry. The seeds are by-products from the processing of fruit-based products, which are normally used for feeding animals and organic fertilizer. We need to recycle huge amounts of guava seed waste by increasing its added values in economics and health. This study aims to prepare hexane extract of guava seed oil (GSO), to analyze its chemical compositions using chromatographic and colorimetric methods, to determine free-radical scavenging activity using colorimetric 2,2-diphenyl-1-picrylhydrazyl (DPPH) and dichlorofluorescein (DCF)-flow cytometric methods, to test its toxicity in cells and animals, and to examine cell migration effect on wound healing. Chromatographic analysis demonstrated that the GSO (yield 6-10 % by weight) was abundant with ω6-polyunsaturated fatty acid linoleic acid (65.95 % of total fatty acid), α-tocopherol (23 mg/kg), β-tocotrienol (70.5 mg/kg), total phenolic compounds (45.57+0.97 mg gallic acid equivalent/g) such as chlorogenic acid and its derivatives and phytosterols such as stigmasterol, β-sitosterol and campesterol. The GSO potently scavenged DPPH radicals (EC50 = 138.83±5.42 mg/mL) and significantly decreased the level of free radicals (100 and 200 µg/mL) in human hepatocellular carcinoma (HepG2) cells in a concentration-dependent manner. Importantly, the GSO also stimulated the migration of cultured skin (HaCaT) cells during wound healing in a concentration-dependent manner with a significant effect at 500 μg/mL. It was non-toxic to peripheral blood mononuclear cells, primary rat hepatocytes and human hepatocellular carcinoma (HepG2) cells, when cultured for 24 and 48 hours, but toxic to human erythroleukemic (K562) cells (IC50 = 155 and 137 μg/mL, respectively). The oil neither induced acute toxicity (LD50 > 10 mg/kg) nor sub-chronic toxicity for up to 90 days in rats. Interestingly, The GSO was found to decrease serum levels of triglyceride, cholesterol and fatty acids in rats. The new findings revealed hexane extract of guava seed oil, which was rich in nutraceuticals included linoleic acid, tocopherols, tocotrienols, phytosterols and phenolic compounds, exerted antioxidant, in vitro free-radical scavenging and anti-cancer activities, wound healing and hypolipidemic effects, indicating the health benefits.