No abstract

Psidium guineense Sw. (Myrtaceae) is a shrub distributed all over South America and Brazil. Its leaves are traditionally used to treat digestive problems and infections. Several biological activities have been reported for P. guineense extracts, however phytochemical studies are scarce. The present study is on the isolation of compounds from P. guineense leaf extracts using chromatographic and spectroscopic techniques and evaluation of their antibacterial activity.Araçain, a tyrosol derivative was isolated as a natural product for the first time.Other compounds isolated were ursolic acid, a phaeophorbide and three flavonoids. The extracts were tested for their antimicrobial activity against Klebsiella pneumoniae strains and they showed moderate to high antibacterial activity.

Species of the Myrtaceae family are widely distributed in the southern hemisphere and include species of high economic value, such as "eucalipto" (Eucalyptus spp.), "goiaba" (Psidium guajava), and others still less exploited, such as Psidium araça Raddi (araçá), species studied in the present work. Previous nutritional evaluations have shown that the araçá fruits, appreciated as food, have low caloric value, high humidity and high levels of calcium and fibers. Its leaves are traditionally used in antidiarrheal preparations, as diuretic, against indigestion and in slurries, due to the high content of tannins. Despite the medicinal and food use, there are only preliminary phytochemical studies with the species. The present work aimed to isolate and identify secondary metabolites of P. araça species. For this purpose, the aerial parts of P. araça were collected in Areia city -PB, identified by Prof. Leonardo P. Félix. The material was dried, ground and macerated with hexane, ethyl acetate and methanol, followed by evaporation of each solvent in a rotary evaporator to obtain the hexane, ethyl acetate and methanol extracts. The methanol extract was chromatographed successive times in Sephadex column using methanol as mobile phase. The obtained fractions were analyzed in thin layer chromatography to combine fractions or to evaluate their purity. From this procedure two fractions were purified and submitted to NMR analysis using deuterated DMSO and acetone. The obtained compounds were identified as the flavonoids quercetin and kaempferol, reported for the first time in the studied specie.

Phenolic compounds have been related to several beneficial effects on health. Most of them are due the antioxidant activity played by these natural occurring substances. The phenolic compounds are able to inhibit the formation of free radicals, which can induce oxidative damage to cell biomolecules, being related to the etiology of several diseases. Many compounds from secondary metabolism of plants can play relevant role in human health preventing cell oxidative damage. The present study was carried out with the vegetal specie PavoniaglaziovianaGürke (Malvaceae), known as "malva-da-chapada" and "tampa-cabaça". Chemotaxonomic studies on the family indicated that its species are great producers of phenolic substances, such as phenolic acids, flavonoids, tannins and coumarins. From the species P. glazioviana the isolation of flavonoids has already been reported. The present aimed to quantify the total phenolic content in the ethanolic extract of P. glazioviana as well as to evaluate the antioxidant potential of the studied species. For this purpose, the dried aerial parts of the plant were extracted with ethanol, followed by evaporation of the solvent in a rotary evaporator. In order to quantify the total phenolic content in the obtained extract, the Folin-Ciocalteau spectrophotometric method was carried out. The DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenger method was used to evaluate its antioxidant activity. After analysis, the obtained result was 48.4 mg of EAG/g of ethanolic extract of the species. In the evaluation of the antioxidant activity, the EC50 found was 6.36 mg/mL ± 0.02921. The obtained results indicated that the specie P. glazioviana produces SciForum high content of phenolic substances and presents interesting antioxidant activity, being higher than other species of Malvaceaepreviously analyzed.