Estudo químico e biológico das flores de Cassia bakeriana Craib

Abstract

Cassia bakeriana Craib is a plant belonging to the Leguminosae-Caesalpioideae family, native to Thailand and adapted to the Cerrado biome. The work aimed to study the chemical composition of C. bakeriana Craib flowers, as well as explore the antifungal, antibacterial, antioxidant, antiglycation, cytotoxic potential and identify the chemical constituents of the most active samples. Chemical prospection of extracts and flower partitions indicated the presence of terpenes, steroids, sugars, phenols, flavonoids and anthraquinones. The chemical composition of the flowers n-hexanic partition (P-HF) was determined by GC-MS, enabling the identification of 11 compounds: five long-chain esters (5; 45%), two long-chain fatty acids (2; 18%), two long-chain alkanes (2; 18%) and two terpenes (2; 18%). Through HPLC-EM-IES analysis, it was possible to identify in the ethanol extract of the flowers (EEF) and in the hexane partition of the flowers (P-HF), dichloromethane partition of the flowers (PDF), ethyl acetate partition of the flowers (P-AEF), n-butanol partition of flowers (PBF), water partition of flowers (P-AF) phenolic compounds and derivatives, flavonoids, anthraquinones and fatty acids. In the quantification of the contents of polyphenolic compounds, the best contents for phenols were found for the ethanol extract (123,4±1.2 mg EAG/gextrat) followed by the partition of ethyl acetate 95,4±0.6 mg EAG/gextract, for proanthocyanidins with n-butanol (92,9±0.0 mg EC/gextract) and for flavonoid content, the ethanol extract (109,6±0.4 mg EQ/gextract), followed by ethyl acetate partition with (128,6 ± 0.6 mg EQ / gextract). The antifungal and antibacterial evaluation was carried out using the Broth Microdilution Method, against Candida species and against bacteria from the oral cavity, respectively. The most active partitions against Candida tropicalis and Candida glabrata were P-HF, P-DF, P-BF, and P-AF with MIC values ranging from 2,9 to 11,72 μg ml-1. For the antibacterial activity, it was considered moderate for the P-DF and P-BF partitions, with a MIC of 50 μg ml-1 for both partitions, against the bacteria A. naeslundii. The evaluation of the antioxidant activity was carried out by the ORAC, DPPH and FRAP methods. Among the partitions, P-AEF had the best result (IC50 of 9,8 ± 0,4μg L-1), demonstrating remarkably high antioxidant activity in all tested methods, with results superior to the positive control ascorbic acid (1317,2 ± 11,3 μmol Trolox eq/gsample). Regarding the glycation inhibition capacity, again the P-AE presented a higher percentage of glycation inhibition (IC50 38,6 ± 0.4 μg mL–1) equal to the positive control (quercetin). The selectivity index (SI) indicated that the extracts and partitions of C. bakeriana Craib flowers did not show any cytotoxicity to Vero cells at the tested concentrations. These findings are auspicious since the use of this polyphenols-rich fractions in further “in vivo” assays could be feasible. In addition, the data from this study extends the mapping of knowledge of this plant species studied by our research group, contributing to its conservation and protection in the Cerrado biome