Aims: To determine the antimycotic and cytotoxic activities of partially purified propolis extract on yeasts, xylophagous and phytopathogenic fungi.
To compare these activities with pinocembrin and galangin isolated from this propolis and with the synthetic drugs ketoconazole and clortrimazole.
Methods and Results: Ethanolic propolis extract was partially purified by cooling at −20°C. Two of its components were isolated by HPLC and identified as pinocembrin and galangin. The antifungal activity was assayed by bioautography, hyphal radial growth, hyphal extent and microdilution in liquid medium. Cytotoxicity was studied with the lethality assay of Artemia salina. The obtained results were compared with the actions of ketoconazole and clortrimazole.
The results showed that the antifungal potency of ketoconazole and clortrimazole is higher than pinocembrin, galangin and the partially purified propolis extract in this order. Otherwise, the cytotoxicity of the synthetic drugs is also the highest.
Conclusions: Partially purified propolis extract inhibits fungal growth. The comparison of its relative biocide potency and cytotoxicity with synthetic drugs and two components of this propolis (pinocembrin and galangin) showed that the propolis from ‘El Siambón’, Tucumán, Argentina, is a suitable source of antifungal products.
Significance and Impact of the Study: The partially purified propolis extract and its isolated compounds, pinocembrin and galangin, have the capacity of being used as antifungals without detriment to the equilibrium of agroecosystems. The impact of this study is that the preparation of agrochemicals with reduced economic costs using a partially purified preparation as the active principle is possible.
Aims: To determine the antibacterial and cytotoxic activities of aqueous and ethanolic extracts of northwestern Argentinian plants used in folk medicine. To compare the mentioned activities with those of five commercial antibiotics. To identify the compounds responsible for the antibacterial activity.
Methods and Results: Plant extracts were prepared according to traditional uses in northwestern Argentina. Antibacterial activity was assayed by agar dilution in Petri dishes and broth dilution in 96‐well plates. Lethal dose 50 (LD50) was determined by the Artemia salina assay. Phytochemical analysis was performed by sample adsorption on silica gel, thin‐layer chromatography (TLC), bioautography and UV‐visible spectra. The results showed that Tripodanthus acutifolius aqueous extracts have lower minimal inhibitory concentrations (MIC) (502 and 506 μg of extracted material (EM) per ml for infusion and decoction, respectively) than cefotaxim MIC (640 μg ml−1) against Acinetobacterfreundii (303). These data were lower than their LD50. Tripodanthus acutifolius tincture showed lower MIC (110 μg of EM per ml) and minimal bactericidal concentration (MBC) (220 μg of EM per ml) than cefotaxim (MIC and MBC of 320 μg ml−1) for Pseudomonasaeruginosa. This extract also showed a MIC/MBC of 110/220 μg of EM per ml, lower than oxacillin (MIC/MBC of 160/220 μg ml−1) for Staphylococcus aureus (ATCC 25923). The cytotoxicity of all extracts were compared with that of commercial antibiotics. Rutin (3,3′,4′,5,7‐pentahydroxyflavone 3‐β‐rhamnosilglucoside), iso‐quercitrin (3,3′,4′,5,7‐pentahydroxyflavone 3‐β‐glucoside) and a terpene would be partially responsible for the antibacterial activity of T. acutifolius infusion.
Conclusions: Tripodanthus acutifolius extracts had the ability to inhibit bacterial growth. The antibacterial activity differs with the applied extractive method, and it could be partially attributed to glycoflavonoids. This paper contributes to the knowledge of antibacterial capacity of plants from northwestern Argentina.
Significance and Impact of the Study: These antibacterial activities support further studies to discover new chemical structures that can contribute to alleviate or cure some illnesses.
Aims: To perform an activity‐guided purification, identification and quantification of antibacterial compounds from Tripodanthus acutifolius infusion. To validate the antibacterial activity of purified substances.
Methods and Results: Bioautographic methods were employed as screening assays for purifying bioactive substances. Purification procedures included sephadex LH‐20 column chromatography and reverse phase HPLC. Identification was achieved by spectroscopic methods (UV‐Vis, MS, NMR and polarimetry) and chromatographic assays (paper chromatography and HPLC). Antibacterial activity was studied by microdilution, colony count and photometric assays, Sytox green stain and transmission electron microscopy (TEM). Four glycoflavonoids (rutin, nicotiflorin, hyperoside and isoquercitrin) and an unusual phenylbutanoid glycoside (tripodantoside) were purified and identified. Tripodantoside was found at 6·59 ± 0·82 g per 100 g of dry leaves. The flavonoids showed bactericidal effect at a concentration of 4 mg ml−1 against Staphylococcus aureus and Pseudomonas aeruginosa strains from American Type Culture Collection, while tripodantoside was almost four times more active than those compounds, with a minimum bactericidal concentration = 1·024 mg ml−1 against these strains. Tripodantoside aglycone showed bacteriolytic effects on the assayed strains, causing evident damages on cell wall and membrane, while tripodantoside did not exhibit those effects.
Conclusions: The antibacterial activity of T. acutifolius infusion would be partially attributed to the purified glycoflavonoids and mainly to tripodantoside.
Significance and Impact: The high extraction yield and the antibacterial activity exhibited by tripodantoside makes this chemical structure of interest to support further studies dealing with chemical modifications to increase the antibacterial activity or to seek another activities.
The composition of honey samples of Plebeia wittmanni (n = 10) and Tetragonisca angustula fiebrigi (n = 12) was analysed. The colours of all collected honeys were amber to dark amber and the pH varied. Moisture was lower than reported for other stingless bee honeys. Conductivity and ash content of P. wittmanni honey were higher than for T. angustula fiebrigi. Acidity of P. wittmanni honey was the highest ever mentioned for all other Plebeia species. Total sugars and sucrose were higher in T. angustula fiebrigi than in P. wittmanni honey. T. angustula fiebrigi honey showed the highest sucrose content ever mentioned and was rich in oligosaccharides. Both honeys split off sucrose, α-glucosides, trehalose, and amylose. The strongest hydrolytic activity was on sucrose, with high activity for T. angustula fiebrigi honey. Raffinose was also hydrolyzed. The honey of both bees inhibited bacterial growth. These properties support, at least in part, the medicinal use of the stingless bee honey by native people. Tetragonisca angustula fiebrigi / Plebeia wittmanni / Meliponini / composition / honey / antibacterial properties Corresponding author: M.A. Vattuone,
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