Extraction and evaluation of antioxidant capacity of total phenolics from lychee (Litchi chinensis L.) seeds
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Date
2018
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CCSHAU
Abstract
Lychee seed, being a biowaste, is an inexpensive source of a variety of polyphenols. However, extraction yield/efficiency of total phenolics from lychee seed powder (LSP) depends on extraction conditions. Hence, in present study, optimum conditions for extraction of phenolics from LSP were deduced using one-factor-at-a-time approach followed by response surface methodology (RSM). The factorial, axial and center point experiments of central composite rotatable design (CCRD) of RSM were carried out to investigate the linear, quadratic and interactive effects of three independent variables namely volume of extractant (ml/g), agitation rate (rpm) and extraction time (min) on the yield of phenolics. Regression analysis showed that ~92% of the variation could be explained by the model. Software mediated numerical optimization was done with the constraint of minimum volume of extractant and extraction time separately for maximum yield of TPC. The experimental values were in accordance with the predicted values, indicating the adequacy of model and success of RSM in optimizing the extraction conditions.
Lychee seed extract (LSE) was analyzed for profiling of phenols and fatty acids using H-UPLC and GC, respectively. Despite reported phenolic compounds, we found new phenolics namely apigenin, catechol, catechin, chlorogenic acid, diadzein, salicyclic acid, trans-ferulic acid, trans-sinapic acid and vanillin in LSE. Among six different fatty acids identified, oleic acid and linoleic acid were abundant. Further, LSE was assayed for its antioxidant activities using an array of tests including free radical scavenging activity, nitric oxide scavenging activity (NOSA), hydroxyl radical scavenging activity, metal chelation activity, total antioxidant activity (TAA), total reducing power (TRP), lipid peroxidation inhibition activity (LPIA) and protein oxidation inhibition activity. Prokaryotic and eukaryotic DNA damage protective efficacy of LSE was also observed using pBR322 plasmid and human lymphocytes, respectively. Results of various experiments showed substantial antioxidant activity of LSE and advocate its exploitation as a source of natural antioxidants to counter ROS-induced pathologies or diseases.
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