COMPARISON BETWEEN CONVENTIONAL AND ADVANCED METHODS OF EXTRACTION ON THE POLYPHENOL CONTENT AND ANTIOXIDANT ACTIVITY OF JAMBOLAN FRUITS (SYZYGIUM CUMINI L.)

Jambolan (Syzygium cumini L.) is a fruit widely distributed in Brazil, mainly in the Northeast and its extracts have been reported as potential antioxidant and food colorant additives due to its phenolic composition, which includes phenolic acids, and flavonoids such as anthocyanins. Conventional methods for polyphenols extraction require extended extraction times and/or high temperature, which can lead to partial degradation of the bioactive compounds. Ultrasound-assisted extraction (UAE) is a technique known to reduce extraction time, solvent usage and increase yield. This study aimed to compare three polyphenols extraction techniques: heated bath extraction (HBE) at 70°C/2 h; exhaustive centrifugation (EC) at 2540xg at 25°C/20 min each run until the residue became colorless; and UAE at 40 KHz, 135W at approximately 30°C/ 20 min. Acidified ethanol 70% was used as solvent at the proportion of 1:25 (g of dried fruit-DF/mL of solvent). A comparison of these methods was performed using Folin-Ciocalteu assay to determine the total phenolic compounds (TPC) content, the results were expressed as mg Gallic Acid equivalent per gram of dry fruit (mg GAE/g DF). pH differential method was used to measure total monomeric anthocyanin (TMA) content, the results were expressed as cyanidin-3-O-glucoside equivalent (mg c3g/g DF). ABTS radical scavenging assay was performed to investigate the effect of the extraction method on antioxidant potential. No statistical difference (p<0.05) was found between the three methods regarding TPC content (HBE: 17.01 ± 0,55 mg GAE/g DF; EC: 16.86 ± 0,63 mg GAE/g DF; UAE: 17.75 ± 0,44 mg GAE/g DF). However, by evaluating the TMA content (HBE: 4.73 ± 0,13 mg c3g/g DF; EC: 5.61 ± 0,32 mg c3g/g DF; UAE: 5.97 ± 0,25 mg c3g/g DF), the results differed significantly (p<0.05) between EC and HBE and UAE and HBE, which implies that the temperature of the heated bath favors the extraction of certain types of polyphenols whereas increases degradation of anthocyanins, which also suggests that the extracts obtained by different methods might also present differentiated phenolic profiles. Although there was no statistical difference (p<0.05) between the TMA content of the EC and UAE methods, UAE reached the same anthocyanin content in 1/3 of the EC extraction time. The extracts showed strong antioxidant activity, where the amounts that reduced antioxidant activity by 50% (IC50) were equal to 0.18 mg/mL for HBE, 0.20 mg/mL for EC, and 0.21 mg/mL for UAE, which correspond to values found in studies with hydroalcoholic extracts from other parts of this fruits, such as the seeds (ABTS IC50= 0,10 mg/mL). These findings reveal that jambolan extracts by HBE, EC, and UAE have remarkable bioactivity, presenting a great potential to be used as natural food additives. However, UAE was the fastest and more efficient extraction method for obtaining extracts rich in anthocyanins and other polyphenols with strong antioxidant activity.