Chemical composition and in vitro antioxidant and antihyperglycemic activities of clove, thyme, oregano, and sweet orange essential oils

Reactive oxygen species and development of hyperglycemia underlie the most prevalent non-communicable chronic human diseases. Thus, the use of natural products, including essential oils, to control these processes has been the subject of many studies. This study aimed to elucidate the chemical composition of essential oils of clove, thyme, oregano, and sweet orange, characterize their antioxidant activity toward 2,2-diphenyl-1-picrylhydrazyl, hydroxyl, and nitric oxide radicals, and assess their antihyperglycemic potential, inhibiting the digestive enzymes alpha-amylase and alpha-glucosidase in vitro. The major compounds found in clove, thyme, oregano, and sweet orange essential oils were eugenol, thymol, 4-terpineol, and D-limonene, respectively. The clove essential oil shower a higher percentage of inhibition of hydroxyl radicals and nitric oxide, while the thyme essential oil displayed greater antioxidant activity toward the radical 2,2-Diphenyl-1-picrylhydrazyl compared with the other oils assessed in this study. In assays of inhibition of digestive enzymes related to development of hyperglycemia, thyme essential oil showed the greatest capacity to inhibit alpha-amylase, while sweet orange essential oil displayed the most potent inhibition of alpha-glucosidase. These results demonstrate the potential for use of these essential oils to prevent and/or treat diseases arising from oxidative stress, such as diabetes mellitus.