In vitro anti-inflammatory and antioxidant properties of peel extract of selected fruits of the citrus family

Abstract

The potential of citrus peel extract in delivering anti-inflammatory and antioxidant properties were evaluated using in-vitro assays. Methanolic extracts of freeze dried peels of Ambul Dodam – Citrus aurantium, Lime – Citrus aurantifolia, Jama naaran – Citrus reticulata, Nas naran – Citrus madurensis, Heen naran - Citrus reticulata were assessed using Lipoxygenase inhibitory assay, Folin-Ciocalteau assay and DPPH radical scavenging assay. The lipoxygenase enzyme inhibition of all citrus varieties were analyzed using two different concentrations 50 μg /mL and 75 μg /mL of peel extracts. The lipoxygenase inhibition levels were within the range of 7.97 % to 23.64 % for 50 μg /mL concentration of peel extracts. The lipoxygenase inhibition levels for 75 μg /mL concentration of peel extract were 6.98 % to 17.99 %. For both concentrations, the highest inhibition (23.64 ± 1.96 % for 50 μg /mL and 17.99 ± 2.48 % for 75 μg /mL) was recorded for Heen Naran. Accordingly, the ascending pattern of percentage lipoxygenase enzyme inhibition for all citrus varieties was: Lime < Jama Naran < Nas Naran < Ambul Dodam < Heen Naran. According to the Folin-Ciocalteau assay the total phenolic contents of Nas Naran and Jama Naran were 471.00 and 1394.00 μg gallic acid equivalent per g dry weight of peel, respectively. DPPH radical scavenging activity of peel extracts of selected citrus fruit varieties ranged from 33.96 to 91.44 %. The percentage inhibition of DPPH radical for citrus peel extracts varied according to the order: Lime < Nas Naran < Heen Naran < Jama Naran < Ambul dodam. High percentage of DPPH radical inhibition may be due to the presence of higher phenolic content. Therefore, it can be concluded that the peels of the evaluated citrus species are having significant antioxidant and anti-inflammatory properties. The discovered potentials can be further studied for effective utilization of peel of citrus fruits in the food industry