Antioxidant activity and phenolic content of chestnut (Castanea sativa) shell and eucalyptus (Eucalyptus globulus) bark extracts

摘要

Chestnut (Castanea sativa) shell and eucalyptus (Eucalyptus globulus) bark, waste products of the food and wood industries, respectively, were analysed as potential sources of antioxidant compounds. The extraction yield, the antioxidant activity and total phenols content of the extracts were greater in chestnut shell than in eucalyptus bark for most of the extraction conditions essayed. Extraction of chestnut shell with a 2.5% NaSO aqueous solution led to the highest extraction yield, 25.6%, total phenols, 13.4g gallic acid equivalent/100g oven-dried shell, and FRAP antioxidant activity, 80.7mmol ascorbic acid equivalent/100g oven-dried shell. Extraction with methanol:water (50:50, v/v) provided the best results for eucalyptus bark. The antioxidant activity and the total phenols content of the extracts had a positive linear correlation. FTIR spectroscopy confirmed the higher content of phenolic compounds in chestnut shell extracts compared to eucalyptus bark extracts. Chestnut shell extracts were characterized by the presence of high molecular weight species whereas lower molecular weight species were predominant in eucalyptus bark extracts.