EFFECT OF EXTRACTION CONDITIONS ON POLYPHENOLS, FLAVONOIDS, S-ALLYL CYSTEINE CONTENT AND ANTIOXIDANT ACTIVITY OF BLACK GARLIC EXTRACTS

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Abstract
Black garlic is obtained from fresh garlic (Allium sativum L.) that has been aged for a long time at a high temperature under high humidity. Black garlic exerts metabolic and cardiovascular beneficial effects. In this study, (i) water and various concentrations of ethanol (50 % and 100 %) in water were used as solvent in the extraction of black garlic with different black garlic:solvent ratios (1:5, 1:10 and 1:15 w/v); (ii) the process was investigated in the temperatures ranging of 40 to 80 oC during 30 to 120 minutes, as well as determination of bioactive compounds content (total polyphenols, total flavonoids and S-allyl cysteine content) of all obtained extracts. The antioxidant activity was evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The obtained results indicated that the aqueous ethanol (50 %) extracts presented the highest contents of polyphenols and flavonoids (7.94 mg GAE/g and 3.37 mg QE/g, respectively) and DPPH radical scavenging activity at black garlic: solvent ratio of 1:10 (w/v); while the water extract showed the highest S-allyl cysteine content (76.0 mg/kg) at the 1:10 ratio. The suitable condition for extracting of total polyphenols and flavonoids from black garlic was 60 oC for 90 minutes. With respect to SAC extraction, the suitable temperature and time of 80 oC and 90-120 minutes, respectively were found.

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