Evaluation of anti-oxidative activity and UV absorption potential of the extracts of Aloe vera L. gel from different growth periods of plants

Abstract

Antioxidant assay, ATR-FTIR spectroscopy mediated predominant functional group detection and UV-absorption spectroscopy have been carried out with methanolic extracts of Aloe vera L. gel (gel-extract) from two, three and four-year-old plants in summer season. To explore the seasonal influence gel-extract has also been prepared from three-year-old aloe in rainy and winter season. Gel-extracts from three-year-old aloe in winter exhibited high response at IR and UV absorption spectrum. Maximum transmittance in IR spectrum has been assigned to phenolic OH stretching followed by CH, CO and COC. Total phenols, flavonoids and flavonols content range from 30.11±1.89 to 35.77±1.07μg GAE/mg, 11.00±0.88 to 29.75±0.88μg RE/mg and 7.47±0.31 to 13.87±0.08μg RE/mg, respectively. The contents of total phenolics, flavonoids, flavonols, aloin, and different free radical scavenging, transition metal chelating and Fe3+ reducing are more pronounced in the gel-extracts from three-year-old aloe at winter and summer season. Phenolics concentration and the distribution of aloin in the gel-extract are significantly (p≤0.05) influenced by the growth periods of A. vera. The presence of conjugated double bonds and high abundance of the integral phenolic OH attribute to the UV absorption and antioxidant potential of the gel-extract, respectively. The present work analysis shows that growth periods of A. vera plays a decisive factor in the regulation of antioxidant activity and UV absorption property of the gel-extracts.