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.

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.

The National Agency of Sanitary Vigilance (Anvisa) defines honey as being the natural product produced by bees from flower nectar and/or saccharin exudates of plants. The chemical composition of honey includes sugars, vitamins, minerals, and compounds from secondary metabolism, such as terpenoids and phenolics. The nutritional and medicinal potential of honey make it widely appreciated and commercially exploited. According to Anvisa, the addition of any substance to honey is prohibited, turning the honey into an adulterated product. Thus, the physicochemical analysis is required to ensure the quality of the product. In the present study, five commercial honey samples produced in the Brejo region of Paraíba (Brazil) were analyzed in order to verify possible adulteration or handling problems during product storage or transportation. The Fiehe reaction was performed in order to verify the presence of substances produced by overheating. Lugol reaction was carried out to investigate addition of starch and dextrins, and Lund reaction was performed to verify the level of albuminoid or precipitable substances. Among the samples analyzed, samples II and V showed a positive result in the reaction of Fiehe, indicating the presence of hydroxymethylfurfural, resulting from the degradation of sugars in acidic conditions, mainly when the honey is heated, which can occur during transport or storage. Sample V also presented evidences of adulteration in the Lund and Lugol reactions. Unadulterated honeys promoted the formation of precipitates during the Lund reaction. In sample V the absence of precipitate was observed, which indicates an adulteration/dilution. Sample V also showed evidence of starch addition in the Lugol reaction. The results indicated adulteration in sample V analyzed and heating problems in sample II. The present work emphasizes SciForum the continuous need of physicochemical evaluation to guarantee the quality of these commercial products.