Abstract
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This is a first-time report to evaluate the effect of natural antioxidants, pH, and green solvents upon catechins yield and stability during the active process of extraction from green tea leaves.
Green solvents (model-A) augmented with piperine (PPN) and quercetin (QT) as natural antioxidants (model-B) at different pH 2–6 (model-C) were used to extract catechins from green tea leaves using an ultrasonic extraction process (USE). For quantification of catechins (EC; epicatechins, ECG; epicatechin gallate, and EGCG; epigallocatechin gallate), a green and sensitive UHPLC-MS/MS method was developed and validated.
The UHPLC-MS/MS method showed an accuracy of 98.3–102.6 % within the linearity range of 1–500 ppb for EC (m/z) 289 → 245 → 109, ECG (m/z) 441.2 → 169 → 289, and EGCG (m/z) 457.1 → 169 → 125.1. The general yield (ppb) for EC, ECG, and EGCG was observed with the ranges and sum of (N = 180) 0.06–157.80 and 6696.83, 0.04–316.93 and 12632.60 and, 0.12–584.11 and 26144.83, respectively. Model-C revealed the highest yield for catechins at the lowest pH-2 with an individual catechin yield of EGCG (584.11) > ECG (316.93) > EC (157.80) in CW2. In terms of stability, EGCG was the most unstable catechin whereas, catechins extracted in model-B exhibited more stability (%recovery of 14.70 for EC, 10.55 for ECG, and 5.36 for EGCG in BEP). Moreover, model-B showed the minimal degradation for catechins within the range of 11.81–94.64 (BEP); even the most degradable EGCG was seen with the smallest %loss of 11.81–94.64 at time 24–70 h, as compared to the loss of > 95 % in model-A and C. The ANOVA score for catechins yield was; F11,168 = 61.06 (EC), F11,168 = 66.53 (ECG), and F11,168 = 48.92 (EGCG) (P = 0.00) with mean scores of (M = 94.63, SD = 25.46) for EC, (M = 194.87, SD = 51.41) ECG, and (M = 357.57, SD = 96.80) EGCG in CE2.
A significant effect on catechins yield and stability was observed with the use of natural antioxidants and lowest pH-2.