Optimization of Extraction of Polyphenols and Antioxidants from Sonneratia Apetala (Buch.-Ham.) Fruits

Abstract

Consumers are increasingly aware of diet related health problems and therefore demanding natural ingredients which are expected to be safe and health-promoting. Health benefits of a diet rich in fruits and vegetables are attributed in part to their contents of polyphenols and other antioxidant components. Costal dwellers in several countries largely used the fruit of Sonneratia apetala (Buch.-Ham.) as foods and in treating various diseases. Reportedly, the fruit is a very rich source of health promoting bioactive components such as polyphenols, flavonoids, antioxidants etc. Therefore, the present research was aimed to optimize the extraction of polyphenols and antioxidants from the S. apetala fruits. To optimize the extraction of total polyphenols (TP), flavonoids (TF), DPPH radical scavengers (DRS) and total antioxidants (TA), different solvents (acetone, ethanol, methanol, distilled water or their mixtures), extraction temperatures (10, 30, 40, 55 or 70°C), pH (1, 2, 3, 4, 5, 7 or 9), preextraction heating (30,60,90, 120, 150 or 180°C for 0.5, 1,2 or 4 h) and extraction times (0, 0.5, 1, 2, 5, 10, 20, 40, 60 or 120 h) were applied. The results showed that solvents, extraction temperatures, pH, preextraction heating and extraction times, all have significant effects on extraction optimization. Among the tested solvents, methanol and ethanol extracted the higher amount of TP, TF, DRS and TA at 30°C. But at 30°C, methanol: ethanol (1:1) mixture showed the best extraction efficiencies than ethanol, methanol or other solvent mixtures. When the effect of pH was tested, the increase in pH (from 1 to 3) led to higher yields of TP, TF, DRS and TA, followed by gradual decrease as the pH values increased. It was found that increase in heating temperatures from 30 to 90°C led to higher yields of TP, TF, DRS and TA. But the extraction efficiencies decreased gradually as the heating temperatures increased; while the best heating time found was 1 h. The extraction of TP, TF, DRS and TA also increased significantly with the increase in extraction time (0 to 20 h). However, further increase in extraction time reduced extraction efficiencies. Thus, the optimum condition for extraction of polyphenols and antioxidants from the fruits was found to be preheating at 90°C for 1 h, methanol: ethanol (1:1) mixture as extraction solvent, pH 3, 30°C as the extraction temperature and 20 h as the extraction time. At this condition, optimum amount of TP, TF, DRS and TA were extracted, and the values were 53.8 ± 0.7 mg gallic acid equivalents (GAE), 9.2 ± 0.1 mg (+)-catechin equivalents (CE), 89.6 ± 0.8 mg ascorbic acid equivalents (AAE) and 36.2 ± 0.4 mg AAE per gram powder, respectively. Therefore, the study would help to improve extraction yield of phenolics from the fruits and its utilization in the preparation of functional foods and dietary supplements.