Chemical characterization and evaluation of antioxidant and antimicrobial activities of Litchi chinensis sonn

Abstract

Background: Litchi chinensis is used in traditional Chinese medicine and by Indian medical system. Ethnopharmacological studies show anti-inflammatory, antidiabetic and analgesic activities, among others. However, there are few studies of antimicrobial activity. This study evaluates antimicrobial, antioxidant, and cytotoxicity properties of the lychee's leaves extract (LE) and fractions. Materials and Methods: Extracts were obtained using an exhaustive extraction method with ethanol: Water (7:3 v/v). Subsequently, LE was concentrated in a rotary evaporator. Finally, LE was dried via lyophilization. Fractions were obtained via the partition process. Bioactivity of the LE and fractions (hexane [Hex], ethyl acetate [EtOAc], n-butanol [BuOH], and aqueous [Aq]) from L. chinensis was evaluated through antimicrobial activity using broth microdilution, antioxidant activity via both 1,1-diphenyl-2-picryl-hidrazila assay and ferric reducing capacity and cytotoxicity through 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay. Furthermore, mass spectrometry technique electrospray ionization ion trap mass spectrometry was used to identify the chemical composition of the LE and fractions. Results: Phenolic compounds, such as flavonoids and condensed tannins were the main substances found. Total phenolic and flavonoid contents were higher in EtOAc (541.15 ± 2.4 mg/g and 31.06 ± 0.5 mg/g, respectively). This fraction showed the best results for antioxidant activity (IC50= 3.45 mg/mL) and ferric reducing capacity (20.27% ± 0.11). The LE and fractions showed considerable antimicrobial activity, chiefly against Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, and Proteus mirabilis, with the minimum inhibitory concentration ranging from 50 to 1560 μg/ml. Conclusion: This study revealed that L. chinensis is a source of bioactive compounds potentially useful for pharmaceutical and food industries. Abbreviations Used: LE: Leaves extract, Hex: Hexane fraction, EtOAc: Ethyl acetate fraction, BuOH: n-butanol fraction, Aq: Aqueous fraction, DPPH: 1,1-diphenyl-2-picryl-hidrazila, MTT: 3-(4,5-dimethyl-thiazol-2-yl)-2, 5-diphenyltetrazolium bromide, ESI-IT-MSn: Electrospray ionization ion trap mass spectrometry, IC50: Median Inhibition Concentration (concentration that reduces the effect by 50%), MIC: Minimum inhibitory concentration, MS/MS: Mass spectrometry, MSn: Tandem mass spectrometry, GAE: Equivalents of gallic acid, QE: Equivalents of quercetin, BHT: Butylated Hydroxy Toluene, UV: Ultraviolet, ATCC: American Type Culture Collection, MHB: Mueller Hinton broth, DMSO: Dimethyl sulfoxide, ANOVA: Analysis of variance, CC50: Cytotoxic concentration 50.