Mango seed kernel, a by-product of the processing industry, can be valorized as a potential source of bioactive compounds. Binary mixtures of ethanol and water, used in solid-liquid extraction (SLE), have drawn interest as an effective means of recovering phytochemicals from plant materials because these solvents can be used in food applications and their synergistic effect makes them a superior solvent over their pure counterparts. Total phenolic content (TPC) and HPLC chromatograms of each ethanolic extract revealed that ethanol concentration had a significant effect on phenolic compound recovery, wherein, TPC of mango kernel varied from 18.19 to 101.68 mg gallic acid equivalence (GAE) per gram of sample. Subsequently, the antioxidant activities (AOAc) of the extracts, measured by scavenging activities with the DPPH ? (1,1diphenyl-2-picrylhydrazyl) radical and ferric reducing antioxidant power (FRAP) assay, ranged from 8.19 to 85.45 mmol/L and 3.82-55.61 mmol/L Trolox equivalence, respectively. The solvent containing 50% (w/w) ethanol-water had the highest TPC and exhibited the most potent reducing and radical scavenging activities. With the use of an HPLC-UV/Vis, gallic acid, caffeic acid, rutin and penta-O-galloyl-b-D-glucose were identified to be present in the mango seed kernel. Results show that the mango seed kernel is a viable source of bioactive compounds which can be recovered with water-ethanol binary solvent systems.

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Mango seed kernel (MSK) is a waste material of the mango processing industry and is reported to significantly contain phenolic compounds with anti-oxidative properties. In this work, these compounds are isolated via solid-liquid extraction (SLE) in which solvent mixture design approach was used to evaluate the optimal quaternary solvent ratio in relation to the phenolics content of extracts from MSK. The quaternary solvent is composed of ethanol (E), methanol (M), acetone (A), and water (W). The extraction process was implemented at 40°C for 60 minutes with the ratio between solid and solvent at 1:25. Response surface methodology coupled with simplex lattice design was developed to evaluate the optimal solvent system and their interaction effects on the phenolic compounds content. The linear, two-way, and three-way interaction, except for methanol-acetonewater system, resulted in positive effects on the phenolic compounds content. The response model shows that a quaternary mixture with approximately 3:3:3:1 E:M:A:W ratio provided the highest phenolic content. A Scheffé cubic model sufficiently described the extraction process. The results of this study showed that the extraction of phenolic compounds in MSK via SLE using a mixture of solvents is possible. Higher extraction efficiencies can be achieved by optimizing the SLE process, and the optimum conditions can be applied to produce phenolic extracts with positive antioxidant activity.

Mango seed kernels (MSK), which are waste streams in mango processing industry, are good sources of phenolic compounds with high anti-oxidant, anti-bacterial, and anti-viral properties. These phenolic compounds are reported to have an increasing demand over the years in the quest for healthy ready-to-eat food and nutraceuticals. To recover these compounds from MSK, solid-liquid extraction (SLE) can simply be applied, although there is a knowledge gap in in the systematic exploration of this process for mango-based phenolic compounds. In this work, phenolic compounds were extracted from MSK through SLE using ethanol-water solvent system. A statistical-based approach was used to evaluate and optimize the extraction conditions in relation to yield of phenolic compounds from MSK. The central composite design together with response surface methodology was adopted to assess the effect of extraction temperature (30oC, 45oC, and 60oC) and ethanol concentration (25% – 75%) under fixed extraction time (105 min) and solid-to-solvent ratio (1:10) on the extraction yield. Both temperature and ethanol concentration provided positive effects on the yield and the following optimum conditions of temperature and ethanol concentration were obtained at 63.21oC and 53.21% ethanol, respectively. A second-order polynomial equation was obtained describing the extraction process, and a validation test of this response model showed that it sufficiently described the process. Furthermore, the extracts obtained at optimal conditions possess a potential antioxidant activity at IC50 = 45 ± 0.002 µg GAE mL-1 extract. The results indicated that phenolic compounds in MSK can be recovered through extraction using aqueous ethanol. This study also promotes value-addition of a seemingly useless waste material while reducing its health and environmental impact.