Biological activities of benzoquinones from Badula barthesia and Embelia angustifolia.

In our screening program for antihypertensive plant constituents extracts of the leaves and bark of Badula barthesia showed strong in vitro inhibition of angiotensin converting enzyme (ACE). Rapanone (1), 2,5-dihydroxy-3-tridecyl-1,4-benzoquinone, was isolated as an active constituent of the leaves. The IC(50) values of rapanone and three 3-alkyl-2,5-dihydroxybenzoquinones, (2)-(4), (Z)-2,5-dihydroxy-3-(pentadec-8-enyl)-1,4-benzoquinone, (Z,Z)-2,5-dihydroxy-3-(heptadeca-8,11-dienyl)-1,4-benzoqui-none and (Z)-2,5-dihydroxy-3-(heptadec-8-enyl)-1,4-benzoquinone recently isolated from Embelia angustifolia were determined. The following IC(50) ± S.D. values have been obtained (1) 36 ± 4.6 µM, (2) 19 ± 6.2 µM, (3) 19 ± 8.7 µM and (4) 16 ± 3.0 µ.M. The IC(50) value for the reference compound Captopril was determined to 12 ± 2.6 nM. The antimicrobial activity of the four compounds was determined by thin layer chromatography agar overlay technique as minimum growth inhibitory amount in µg. One yeast, Candida albicans, and four bacteria, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were used as test organisms.

Antimicrobial screening of selected medicinal plants from India.

From the Indian traditional medicines 78 plants were selected on the basis of their use in the treatment of infectious diseases. Different concentrations of 80% ethanol extracts were tested, using the agar dilution method, against four bacteria: Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa and, using the agar-well diffusion method, against two fungi: Candida albicans and Aspergillus niger. In the lowest tested concentration of 1.6 mg/ml, 10% of the plant extracts were active; 44% in a concentration of 6.25 mg/ml and 90% of the plant extracts were active against at least two bacteria in a concentration of 25 mg/ml. Only 13% of the plant extracts were active against at least one fungus in a concentration of 50 mg/ml.

New anti-HIV-1, antimalarial, and antifungal compounds from Terminalia bellerica.

A bioactivity-guided fractionation of an extract of Terminalia bellerica fruit rind led to the isolation of two new lignans named termilignan (1) and thannilignan (2), together with 7-hydroxy-3',4'-(methylenedioxy)flavan (3) and anolignan B (4). All four compounds possessed demonstrable anti-HIV-1, antimalarial, and antifungal activity in vitro.

Plants from Réunion Island with alleged antihypertensive and diuretic effects--an experimental and ethnobotanical evaluation.

Eighty species of vascular plants were collected on Reunion Island and tested for their ability to inhibit the angiotensin converting enzyme (ACE), which plays an important role in the regulation of blood pressure and diuresis. Of these species, 26 serve as antihypertensive remedies in traditional medicine, and 38 as diuretics-10 of the 64 species have both alleged antihypertensive and diuretic effects. Of the species examined, 26 have not been reported to have any of these effects. Plant material was extracted with both acetone, ethanol and water, and samples were considered active if ACE inhibition was 50% or more in one of the extracts. Of the species with alleged antihypertensive or diuretic effect, 44% proved active. Of the species with no report of such effects, 31% proved active. There were no overall differences in the range of inhibition of the three extracts, but amongst the species considered active there was a strong negative correlation between inhibition of acetone and water extracts. A statistical analysis of the results demonstrated clear differences between plants with alleged antihypertensive effects, diuretic effects, and no alleged use with respect to inhibition of the three extracts.

Angiotensin converting enzyme (ACE) inhibitory flavonoids from Erythroxylum laurifolium.

In our screening program for antihypertensive properties of plants in traditional use, the 99% ethanol extract of Erythroxylum laurifoiium leaves showed interesting angiotensin converting enzyme (ACE) inhibitory activity. The activity was found to be due to proanthocyanidins or condensed tannins and the flavonoids quercetin-3-O-rhamnoside (quercitrin) (IC(50) = 0.67 mM) and kaempferol-3-O-rhamnoside (afzelin) (IC(50) = 2.8 mM). In addition, quercitrin with afzelin demonstrated in vitro synergistic ACE inhibitory activity.

Isolation of an angiotensin converting enzyme (ACE) inhibitor from Olea europaea and Olea lancea.

The aqueous extract of the leaves of Olea europaea and Olea lancea both inhibited Angiotensin Converting Enzyme (ACE) in vitro. A bioassay-directed fractionation resulted in the isolation of a strong ACE-inhibitor namely the secoiridoid 2-(3,4-dihydroxyphenyl)ethyl 4-formyl-3-(2-oxoethyl)-4 E-hexenoate (oleacein) (IC(50) = 26 µM). Five secoiridoid glycosides (oleuropein, ligstroside, excelcioside, oleoside 11-methyl ester, oleoside) isolated from Oleaceous plants showed no significant ACE-inhibition whereas, after enzymatic hydrolysis, the ACE-inhibition at 0.33 mg/ml was between 64% to 95%. Secoiridoids have not been described previously in the literature as inhibitors of ACE. Oleacein showed a low toxicity in the brine shrimp (Artemia satina) lethality test (LC(50) (24 h) = 969 ppm).

In vitro screening of traditional medicines for anti-hypertensive effect based on inhibition of the angiotensin converting enzyme (ACE).

Traditional medicines reported to be used as anti-hypertensives or diuretics from different regions in the world (China, India and South America) have been investigated. The bioassay is based on inhibition of ACE, as measured from the enzymatic cleavage of the chromophore-fluorophore-labelled substrate dansyltriglycine into dansylglycine and diglycine. In total, 31 species have been investigated and the crude extracts from seven species inhibit the enzyme by more than 50%.