Abstract
The antimicrobial, antioxidant, and anticholinesterase activities of ethanolic seed extracts of twenty-one plant species from Brazilian semiarid region were investigated. The extracts were tested for antimicrobial activity against six bacteria strains and three yeasts. Six extracts presented activity against the Gram (−) organism Salmonella choleraesuis and the Gram (+) organisms Staphylococcus aureus and Bacillus subtilis. The MIC values ranged from 4.96 to 37.32 mg/mL. The Triplaris gardneriana extract presented activity against the three species, with MIC values 18.8, 13.76, and 11.15 mg/mL, respectively. Five extracts presented antioxidant activity, with EC50 values ranging from 69.73 μg/mL (T. gardneriana) to 487.51 μg/mL (Licania rigida). For the anticholinesterase activity, eleven extracts were capable of inhibiting the enzyme activity. From those, T. gardneriana, Parkia platycephala and Connarus detersus presented the best activities, with inhibition values of 76.7, 71.5, and 91.9%, respectively. The extracts that presented antimicrobial activity were tested for hemolytic assay against human A, B, and O blood types and rabbit blood. From those, only the Myracrodruon urundeuva extract presented activity (about 20% of hemolysis at the lowest tested concentration, 1.9 µg/mL). Infrared spectroscopy of six representative extracts attested the presence of tannins, polyphenols, and flavonoids, which was confirmed by a qualitative phytochemical assay.
Highlights
Plants are considered natural sources of new compounds of medical and biotechnological interest, since they synthesize a large variety of bioactive compounds
The species T. gardneriana showed the broadest spectrum of activity, being active against B. subtilis, S. choleraesuis, and S. aureus with Minimum Inhibitory Concentration (MIC) values of 18.8, 13.76, and 11.15 mg⋅mL−1, respectively
As to the potency of the antibacterial activities observed, these were much lower than those described for Syzygium jambolanum seed extracts against the same bacterial strains used in this work (MIC values ranging from 0.06 to 0.25 mg⋅mL−1), even when compared to the best result observed as described above for S. obtusifolia (MIC 4.96 mg⋅mL−1)
Summary
Plants are considered natural sources of new compounds of medical and biotechnological interest, since they synthesize a large variety of bioactive compounds. Well-known examples of these compounds include flavonoids, phenols and phenolic glycosides, unsaturated lactones, sulphur compounds, saponins, cyanogenic glycosides, and glucosinolates [4,5,6] In this context, the Brazilian semiarid region is a rich and underexploited source of bioactive molecules. The Brazilian semiarid region is a rich and underexploited source of bioactive molecules This area is covered mainly by xeric shrublands known as “Caatinga.” This dry land vegetation grows over an area of 800,000 km in Northeastern Brazil, and out of 1,000 vascular plant species described many are endemic [7, 8]. A hemolytic activity assay was done for antibacterial samples to assess the effects on nontarget cells
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