The aim of this study was to quantify and evaluate the antibacterial activity of tannins extracted from leaves of Psidium guineense, obtained using two different isolation methods, against Staphylococcus aureus and Pseudomonas aeruginosa. The first extraction method was used to isolate condensed tannins (Method A) and the second to isolate mixtures rich in esters of gallic acid and glucose (Method B). Both extraction methods yielded high concentrations of tannins, with 312 and 257 mg/g of dry material obtained using Methods A and B, respectively. These compounds formed halos of growth inhibition in S. aureus and P. aeruginosa cultures. Tannins isolated by method B gave rise to larger inhibition halos than those isolated by method A. Analysis of the antibacterial activity of tannins isolated by method B revealed a minimum inhibitory and bactericidal concentration of 256 μg/ml for S. aureus and 512 μg/ml for P. aeruginosa. These results demonstrate that P. guineense is a promising source of pharmacologically active tannin molecules, and further studies are therefore necessary to determine the toxicity of the plant and ensure its safe use for animal and human health.
Leaves of Anacardium humile are used in Brazilian traditional medicine for the treatment of intestinal disturbances and skin lesions. This study aimed to define leaf diagnostic structural characters, to propose a new method of phytochemical analysis of secretions, prospect flavonoids and alkaloids, and to evaluate their inhibitory activity on Candida albicans. Common anatomical, phytochemical, and microbiological methods were used. Leaves of Anacardium occidentale were used as a reference for the structural analyses. The main structural characters were closed vascular system, absence of ducts at the medulla, bilateral mesophyll, absence of bundle sheath extension, and secretory idioblasts at the xylem. The ducts present schizogenous origin, and secreting activity is restricted to the initial phases of leaf blade expansion. The proposed new phytochemical method is practical and inexpensive and has potential for wide application. The abundance of tannins and flavonoids is related to medicinal use. A single peak in high-performance liquid chromatography indicated the presence of a pure substance not previously reported. The extract had a strong inhibitory effect on C. albicans. The obtained results confirm the potential of A. humile for the prospection of new bioactive compounds.
The bark of the underground stem of Tontelea micrantha (Mart. ex. Schult.) A. C. Sm., a native Brazilian Cerrado species, is used in folk medicine for treating kidney ailments. The structures of the underground and the aerial stems were examined and their barks were analyzed for the presence of secondary metabolites. Bark fragments were processed according to conventional techniques in plant anatomy and their chemical compositions examined using histochemical and phytochemical tests, thin layer chromatography, and high-efficiency liquid chromatography. The underground stem is a sobol with unusual cambial activity. Laticifers that secrete terpenoids were present in the cortex and phloem of both organs and can contribute to the identification of the species in field. Druses were present in both barks, but mono-crystals were only observed in the sobol. Tannins, flavonoids, alkaloids, and terpenoids occurred in both types of bark, but carotenoids were only detected in the sobol. The similarities between these two organs indicate that the aerial stem bark has potential medicinal use and represents a plausible alternative to harvesting the sobol, which could contribute to the preservation of natural populations of this species.
In vitro tests conducted with extracts rich in tannins have identified several biological activities of this class of substance. Thus, this paper intends to evaluate the antibacterial activity of tannin-rich fraction obtained from leaf extracts of
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