Extraction optimitization, chemical composition and biological activities of two types of Solanum gilo Raddi

Abstract

Solanum gilo Raddi is a highly esteemed vegetable in the southeastern region of Brazil, especially in the State of Minas Gerais. This work was carried out with two types of S. gilo named Long Light Green (LLG) cv. Tinguá and Spherical Dark Green (SDG) cv Morro Grande. It was divided in three chapter. For that, seeds of two types of S. gilo were cultivated in open field in order to obtain the immature fruits. In the first chapter, aimed to evaluate the nutritional and nutraceutical composition. The results shows significant differences between them. Both type of S. gilo fruits showed considerable mean of sugar fraction (6.85 g 100g-1); vitamin C (21.62 mg 100g-1); soluble pectin fiber (70.69 mg 100g-1) and total soluble fiber (985.19 mg 100g-1) contents, together with substantial amount of mineral like boron, copper, magnesium, zinc and iron support its nutritional importance to human health. Furthermore, for both type, the chlorogenic acid was the major phenolic acid and accounted for more than 50% of the chromatogram peak area. Its content was significantly higher in SDG (29.05mg g-1 crude extract), compared to LLG (21.85 mg g-1 crude extract). In the second chapter, we investigate the influence of different parameters (extraction methods, ethanolic grade and extraction time) in to order to maximize the extraction yield of total polyphenols and flavonoids contents and the antioxidant potential of two types of S. gilo, using response surface methodology (RSM) for data analysis. The results showed that the most significant variable in the extraction procedure was solvent concentration. The optimal conditions for maximum total polyphenols compounds (TPC), total flavone/flavonol (TFF), and total flavanone/dihydroflavonol (TFD) yields were 68%, 81% and 53% ethanol respectively, with a 30 min extraction time, except for TFD which need less time of extraction (17 min). In the last chapter, aimed to evaluate the effect of extraction methods, sonication (SO), turbo-extraction (TE) and dynamic maceration (DM) on the TPC, TFF and TFD contents, chlorogenic acid content by HPLC and antioxidant activities of 70% hydroalcoholic extracts, from both S. gilo types. The SDG type had higher amounts of chlorogenic acid in all extraction method. The DM-extract was the most effective for recovery chlorogenic acid whereas SO-extract achieved the lowest amounts. TPC and TFF content were higher in SDG type, ranging from 7.68±0.60 to 8.61±0.32a mgGAE g-1 and from 0.15±0.02 to 0.32±0.01 mgQE g-1, respectively. For which the TE-method were the best extractive method followed by SO-method. Whereas, LLG type presented higher TFD content that ranged from 7.07±0.15 to 12.17±0.88 mgNE g-1 dry fruit. Independent of extraction method, SDG type extracts showed the best TPC and chlorogenic acid contents, as well the highest potential for scavenging free radicals (ABTS, DPPH), total antioxidant activity and chelating iron metal ions. The SO-extracts presented the highest antioxidant activities (DPPH, CAT and quelating power) while TE-extracts were the best ABTS.+ scavengers. Total phenolic content showed a good correlation with the antioxidant capacity measured using DPPH and ABTS free radical scavenging. In conclusion, our results show that both type of S. gilo (LLG and SDG) can be considered a functional food due to have an expressive content of fibers (soluble pectin), vitamin C, minerals and phenolic compounds and great antioxidant activities.