Antioxidant components and properties of dry heat treated clove in different extraction solvents

The effects of heat treatment and extraction solvents (pure/aqueous acetone, ethanol, methanol) on antioxidant activity (AA) and components of clove (Syzygium aromaticum Linn) were studied. Clove was subjected to dry heat treatment (microwave and roasting) and the AA measured by free radical scavenging activity (FRSA), reducing power (RP), and phospho-molybdenum assay (TAA). Unheated samples served as controls. The antioxidant components estimated were total phenols, flavonoids and tannins. Using RP and FRSA, highest AA was observed in 80 % acetone extract of all samples (1.778–1448 and 84.5–86.0 %). TAA showed higher value in 80 % methanolic extract for all samples in the range 303.595–307.941 mmol ascorbic acid/g. Heated samples exhibited higher AA in all assays. Highest amount of phenols and flavonoids were extracted in 80 % acetone (4053-4064 mg/100 g) and 80 % methanol (11,271–11,370 mg/100 g) respectively. For tannins, maximum extraction was in 80 % acetone (control, 16441 mg/100 g), 80 % ethanol (microwave, 19,558 mg/100 g), and pure methanol (roasted, 15,823 mg/100 g). Total phenol and flavonoid contents were positively associated with AA determined using RP and FRSA. In conclusion, clove exhibited powerful AA in different extraction solvents which increased on dry heat treatments and correlated positively with antioxidant components. Hence, clove can be used as a natural antioxidant in food systems