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

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 C-H, =CO and -COC. Total phenols, flavonoids and flavonols content range from 30.11 +/- 1.89 to 35.77 +/- 1.07 mu g GAE/mg, 11.00 +/- 0.88 to 29.75 +/- 0.88 mu g RE/mg and 7.47 +/- 0.31 to 13.87 +/- 0.08 mu g 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. (C) 2013 Elsevier B.V. All rights reserved.