New bioactive chalcones in propolis from El Salvador

2',3'-Dihydroxy-4,4'-dimethoxychalcone (1) and 2',3',4-trihydroxy-4'-methoxy-chalcone, two new chalcones, were isolated from propolis from El Salvador. The compounds showed significant antibacterial and antifungal activity and moderate toxicity to Artemia salina nauplii.     

GC-MS of Crinum latifolium L. alkaloids

A GC-MS analysis of underivatized alkaloids from leaves of Crinum latifolium was performed. From the identified 15 alkaloids, 9 were found for the first time in this plant. Almost all alkaloids belonged to the crinane type. Substantial changes in the methylation and oxidation pattern of the alkaloids at and after flowering were observed.     

Propolis from the Mediterranean region: chemical composition and antimicrobial activity

The chemical composition of propolis from Bulgaria, Turkey, Greece and Algeria was investigated by GC-MS. All of them contained mainly flavonoids and esters of caffeic and ferulic acids, which indicated that their main source are buds of poplars of the taxonomic section Aegieros. Some Turkish samples contained a low percent of diterpenic acids, while in Algerian samples significant amounts of a hydroxyditerpenic acid (M=322, its structure not determined by its MS) were found. All samples showed significant antibacterial and weak to moderate antifungal activity.     

Effect of stress experienced during pregnancy on the rate of lipid peroxidation in erythrocytes and brain tissue of newborn rat pups

The rate of lipid peroxidation (LPO) in erythrocytes and brain homogenate has been assessed by the accumulation of malondialdehyde, the degree of erythrocyte autohemolysis, the content of hydrogen peroxide and catalase activity observed in newborn rats aged 1 hour, 1, 15, 20 and 30 days. Pregnant rats were exposed to emotional stress (aggressive interaction of two pregnant rats in an unavoidable conflict situation provoked by nociceptive irritation. Significant age-dependent differences in the rate of LPO (both in erythrocytes and cerebral tissue) have been found. The highest rate was noted in rats 15 days of age. The emotional stress of pregnant females resulted in the changes of behavioural reactions of newborn rats and LPO activity that was characterized by the increase in LPO rate in 1-hour- and 1-day-old rats and by slowing of LPO rate in 15-day-old rats. These phenomena were observed in erythrocytes and brain tissues of test animals.     

Volatile substances of the green alga Scenedesmus incrassatulus

Volatile substances of the green microalga Scenedesmus incrassatulus, cultivated in fresh and salt water, were studied. Cultivation in fresh water diversifies volatile secondary metabolites. Hydrocarbons and derivatives of the acetate pathway predominate when algae are grown in salt water; isoprenoids and aromatics are more abundant after fresh water cultivation.     

Chemical composition and biological activity of propolis from Brazilian meliponinae

Twenty-one propolis samples produced by 12 different Meliponinae species were analyzed by GC-MS. Several chemical types of stingless bees' propolis could be grouped, according to the prevailing type of compounds like: 'gallic acid", "diterpenic" and "triterpenic" types. The results confirm that neither the bee species nor the geographical location determine the chemical composition of Meliponinae propolis and the choice of its plant source, respectively. This could be explained by the fact that Meliponinae forage over short distances (maximum 500 m) and thus use as propolis source the first plant exudate they encounter during their flights. The antibacterial, antifungal and cytotoxic activities of the samples were also investigated. Most samples had weak or no activity against E. coli, weak action against Candida albicans. Some of them showed significant activity against St. aureus., presumably connected to the high concentration of diterpenic acids. Samples rich in diterpenic acids possessed also high cytotoxic activity (Artemia salina test).     

Secondary metabolites of Ceratophyllum demersum

Ceratophyllum demersum L. is abundant in European rivers and ponds and produces a large amount of biomass. Almost nothing is known about its secondary metabolites. We isolated two flavonoid glycosides and identified one of them an apigenin-7-O-glucoside. Seven sterols, the main one sitosterol, were also identified. Volatile compounds contained mainly n-paraffins, together with benzyl acetate and a sesquiterpene.     

Antibacterial Compounds from Propolis of Tetragonula laeviceps and Tetrigona melanoleuca (Hymenoptera: Apidae) from Thailand

This study investigated the chemical composition and antimicrobial activity of propolis collected from two stingless bee species Tetragonula laeviceps and Tetrigona melanoleuca (Hymenoptera: Apidae). Six xanthones, one triterpene and one lignane were isolated from Tetragonula laeviceps propolis. Triterpenes were the main constituents in T. melanoleuca propolis. The ethanol extract and isolated compounds from T. laeviceps propolis showed a higher antibacterial activity than those of T. melanoleuca propolis as the constituent α-mangostin exhibited the strongest activity. Xanthones were found in propolis for the first time; Garcinia mangostana (Mangosteen) was the most probable plant source. In addition, this is the first report on the chemical composition and bioactivity of propolis from T. melanoleuca.     

Chemical composition and biological activities of the Black Sea algae Polysiphonia denudata (Dillw.) Kutz. and Polysiphonia denudata f. fragilis (Sperk) Woronich

The two investigated algae had almost identical sterol composition, but there were significant differences in the composition of the polar components and especially in the composition of the volatiles. P. denudata f. fragilis extracts possessed a stronger biological activity (antibacterial, antifungal and toxicity against Artemia salina). Despite the minute morphological differences between the two algae, we recommend P. denudata f. fragilis to be regarded as P. denudata subsp. fragilis.     

Renin-angiotensin-aldosterone system in rats with neurogenic stress]

A moderate neurogenic stress was induced in adult male rats by crowding for a period of 1 and 7 days. The content of angiotensin I and the activity of renin in the blood plasm aldosterone concentration in the peripheral blood plasma considerably. Seven days after the beginning of the neurogenic stress the content of aldosterone in the blood plasma considerably. Seven days after the beginning of the neurogenic stress the content of aldosterone in the blood and the adrenal tissue was determined radioimmunologically. Crowding of rats for 24 hours led to a marked increase of aldosterone content in the adrenal glands, failed to alter the content of this hormone in the blood, decreased the activity of renin and angiotensin I content in the blood and the adrenal glands of rats proved to fall; as to the activity of renin and the amount of angiotensin I in the peripheral blood plasma - it rose. The problem on the causes of dissociation observed in the renin-angiotensin-aldosterone system in response to the neurogenic stress of various duration is discussed.