Dried tempeh is known to be significantly stable to lipid oxidation compared with unfermented soybeans (BS). A new antioxidant was isolated from the methanol extract of tempeh and identified as 3-hydroxyanthranilic acid (HAA) by UV, IR, EI-MS, and 1 H-, 13 C-, HMQC-, and HMBC-NMR techniques. HAA was effective in preventing autoxidation of soybean oil and soybean powder, while 6,7,4‘-trihydroxyisoflavone (a well-known antioxidant) was not. HAA also exhibited strong antioxidative activity in both water/ethanol and rabbit erythrocyte membrane ghost systems. HAA was not found in BS, but was produced during the incubations with Rhizopus oligosporus IFO 32002 and 32003. The amount of HAA reached a maximum at the stage of 2 days (acceptable), which had the strongest antioxidative activity.
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ESAKI et al. (1996) studied this question.
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