Structure elucidation of olasubscorpioside C, a new rotameric biflavonoid glycoside from the stem barks of Olax subscorpioidea (Oliv)

From the n-butanol soluble fraction of the ethanol extract of the medicinal plant Olax subscorpioidea, a previously unreported rotameric biflavonoid glycoside constituted of 4'-O-methylgallocatechin-(4α → 8)-4'-O-methylgallocatechin as aglycone named olasubscorpioside C (1) along with the known 4'-O-methylgallocatechin (2) were isolated. Their structures were determined on the basis of spectrometric and spectroscopic techniques including HRFABMS, ¹ H and ¹³ C NMR, DEPT 135^o , HSQC, HMBC, ROESY, and CD followed by comparison with the reported data.

Elemane-Type Sesquiterpene, Acetonide Derived Polyacetylene and Other Constituents from the Whole Plant of Gymnanthemum theophrastifolium (Schweinf. ex Oliv. & Hiern) H.Rob. and Their Chemophenetic Significance

The chemical investigation of the methanol extract of the whole plant of Gymnanthemum theophrastifolium (Schweinf. ex Oliv. & Hiern) H.Rob. (Asteraceae) led to the isolation of a new elemane-type sesquiterpene (1), a new acetonide derived polyacetylene (2) and a naturally occurring compound (3) from the plant kingdom along with sixteen known compounds (4-19). Their structures were elucidated by extensive NMR and MS analysis. This is the first report on the chemical constituents of G. theophrastifolium. Furthermore, compounds 12, 13, and 14 are reported for the first time from the family Asteraceae, while compound 9 is reported for the first time from the genus Gymnanthemum. Thus, the present results provide valuable insights to the chemophenetic knowledge of G. theophrastifolium, which is also discussed in this work.

Acute and sub-acute toxicity of the aqueous extract from the stem bark of Tetrapleura tetrapteura Taub. (Fabaceae) in mice and rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tetrapleura tetrapteura Taub. is a leguminous multipurpose tree (Fabaceae) indigenous to tropical Africa. Fruits, seeds and stem bark infusions or decoctions of Tetrapleura tetrapteura Taub. are used to treat many diseases, such as gastric ulcer, rheumatism, malaria, hypertension and hyperlipidemia.

AIM OF THE STUDY

This work was conducted to evaluate the acute and sub-acute toxicity of the aqueous extract of Tetrapleura tetrapteura Taub. (AETT) stem barks.

MATERIALS AND METHODS

For the study of acute toxicity, single oral doses of 2000 mg/kg and 5000 mg/kg of AETT were administrated to male and female Balb/c mice, followed by observation of mice for 14 days. In the study of sub-acute toxicity, 48 albino wistar rats of both genders were randomly divided into six groups of 8 animals and they were daily and orally administrated for twenty eight days. The animal's test groups and satellite test group were administrated with the extract (AETT) at the doses of 100, 200 and 400 mg/kg and 400 mg/kg respectively. On the 29th day, the satellite group (control 2 and satellite 400 mg/kg) were observed during two more weeks. General behavior changes, mortality, body weight of animal, water and food intake were recorded during the study period. At the end of each treatment period, biochemical and hematological parameters were measured and histological examinations of liver and kidneys sections performed.

RESULTS

Up to 5000 mg/kg single dose administration of AETT for fourteen days registered no death animal. In sub-acute study, no mortality was recorded in various experimental groups. Significant reductions in body weight, water and food intake were recorded in all treated animals. Relative weights of liver, kidneys, stomach, spleen, lungs, and heart of treated animals remained unchanged. Significant increases in the number of platelets as well as in serum ALAT level were recorded in rats, treated with 400 mg/kg of AETT. Female rat liver histology showed, at a higher dose of AETT, a slight congestion of portal vein.

CONCLUSION

AETT is safe after therapeutic (200 mg/kg) or acute administration. Higher dose (400 mg/kg) administered for longer period showed signs of liver toxicity.

Identification of Ellagic Acid Derivatives from Stem Bark of Syzygium Guineense (Myrtaceae)

An LC-DAD-ESI-MSn technique was developed to investigate crude extracts of the stem bark of S. guineense for phenolic compounds. Ellagic acids were detected on the basis of their UV absorption spectra and ESI-MS fragmentation patterns. Six ellagic acid conjugates in the complex extract of S. guineense were identified. With the aim to confirm the structures, further purification of the extract afforded the known 3-O-ellagic acid-4′-O-α-rhampyranonosides (3), two new ellagic acid rhamnopyranosides, 3-O-methylellagic acid-4′-O-α-2″-O-acetylrhamnopyranoside (4) and 3-O-methylellagic acid-4′-O-α-3″-O-acetylrhamnopyranoside (6). The structures were identified on the basis of 1D- and 2D- NMR, IR, and UV spectroscopic and mass spectrometric data. The HMBC and NOESY data of these compounds were most useful for determination of their structures. Radical scavenging activities were evaluated in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Compounds 3, 4 and 6, with IC50 values of 6.1 ± 0.5, 5.8 ± 0.4, and 6.2 ± 0.4 μM, respectively were as active as ellagic acid (1) (IC50 = 4.9 ± 0.3 μM) and more active than catechin (IC50=10.8 ± 0.3 μM).

Antimicrobial and antioxidant flavonoids from the leaves of Oncoba spinosa Forssk. (Salicaceae)

Background

Naturally occurring flavonoids have been reported to possess various pharmacological properties. The aim of this study was to evaluate the antimicrobial and antioxidant activities of the MeOH extract and flavonoids from the leaves of Oncoba spinosa, a plant used for the treatment of syphilis, wounds and sexual impotence.

Methods

The plant extract was prepared by maceration in methanol and sequentially fractionated by column chromatography. The structures of isolated compounds were elucidated on the basis of spectral studies and comparison with published data. The MeOH extract and its isolated compounds were evaluated for their antibacterial and antifungal activities by broth microdilution method. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays were used to detect the antioxidant activity. The samples were tested spectrophotometrically for their hemolytic properties against human red blood cells.

Results

The fractionation of the MeOH extract afforded five known flavonoids including kaempferol (1), quercetin (2), apigenin-7-O-β-D-glucuronopyranoside (3), quercetin 3-O-β-D-galactopyranoside (4) and quercetin 3-O-α-L-rhamnopyranosyl (1 → 6) β-D-glucopyranoside (5). The MeOH extract displayed weak to moderate antimicrobial activities (MIC = 256–2048 μg/ml). Quercetin 3-O-α-L-rhamnopyranosyl (1 → 6) β-D-glucopyranoside (5) and quercetin (2) were respectively the most active compounds against bacteria (MIC = 8–64 μg/ml) and fungi (MIC = 64 – 128 μg/ml). These tested samples also showed high radical-scavenging activities (EC₅₀ = 5.08 – 70.56 μg/ml) and gallic acid equivalent antioxidant capacities (TEAC = 53.76 – 89.86 μg/ml) when compared with vitamin C (EC₅₀ = 4.72 μg/ml). The MeOH extract and compounds 2–5 were non-toxic to human red blood cells indicating their high selectivity to be used as antimicrobial and antioxidant drugs.

Conclusion

The MeOH extract of O. spinosa as well as compounds 2 – 5 could be a potential source of natural antimicrobial and antioxidant products.

Two new tryptophan derivatives from the seed kernels of Entada rheedei: effects on cell viability and HIV infectivity

Two new tryptophan derivatives, N-sulfonyl-L-tryptophan (tryptorheedei A) (1) and 3-(N-sulfonylindolyl)-D-lactic acid (tryptorheedei B) (2) together with the known 5-O-β-D-glucopyranosyl-2-hydroxyphenylacetic acid (3), 1-O-methylglucopyranoside, entadamide A, homogentisic acid and 3-O-β-D-glucopyranosyl-β-sitosterol, were isolated from the seed kernels of Entada rheedei (Mimosaceae). Their structures were established using 1D and 2D NMR spectroscopy, mass spectrometry and by comparison with spectroscopic data reported in the literature. Compounds 1 and 2 showed no toxicity to TZM and Human PBMC cells. Both compounds 1 and 2 were found to promote early infection events in HIV, likely by inhibiting the enzyme indolamine 2,3-dioxygenase (IDO) and preventing tryptophan depletion. Inhibition of IDO acutely in HIV infection inhibits viral replication, but chronic activation of IDO leads to immune impairment in AIDS. IDO is also the gatekeeper enzyme for kynurenine metabolism, a pathway involved in serotonin and melatonin biosynthesis and the regulation of glutamate and dopamine levels in the brain. Therefore inhibition of IDO might explain both the reported medicinal and neuropsychiatric effects of E. rheedei.

Cycloartane glycosides from leaves of Oxyanthus pallidus

From the MeOH extract of leaves of Oxyanthus pallidus, three cycloartane glycosides, named pallidiosides A-C, were isolated together with two known compounds, oleanolic acid and 3-O-β-D-glucopyranosyl-β-sitosterol. The structures of pallidiosides A-C were assigned on the basis of spectral studies and comparison with published literature data. The known compounds were identified by means of Co TLC and confirmed by their physical constants.

In vivo anti-inflammatory effect of a new steroidal saponin, mannioside A, and its derivatives isolated from Dracaena mannii

A new steroidal saponin, mannioside A (1), was isolated from the stem bark of Dracaena mannii, together with the known pennogenin (2), pennogenin-3-O-beta-D-glucopyranoside (3) and pennogenin-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->3)]-beta-D-glucopyranoside (4). Their structures were determined using 1D-and 2D-NMR spectroscopy and mass spectrometry. Compounds 1 and 3 significantly inhibited carrageenan-induced paw edema in the rat; compound 4 was moderately active whereas 2 showed very weak activity.

Analgesic and anticonvulsant effects of extracts from the leaves of Kalanchoe crenata (Andrews) Haworth (Crassulaceae)

Kalanchoe crenata Andr. (Crassulaceae) is a fleshy herbaceous plant used in the African traditional medicine as remedies against otitis, headache, inflammations, convulsions and general debility. In the present work, the analgesic effects of methylene chloride/methanol (1:1) (CH(2)Cl(2)/CH(3)OH) extract and its hexane, methylene chloride (CH(2)Cl(2)), ethyl acetate, n-butanol fractions and aqueous residue have been evaluated using acetic acid, formalin and pressure test. The anticonvulsant effects of the CH(2)Cl(2)/CH(3)OH extract were also investigated on seizures induced by pentylenetetrazol (PTZ 70 mg/kg), strychnine sulphate (STN 2.5 mg/kg) and thiosemicarbazide (TSC 50 mg/kg). CH(2)Cl(2)/CH(3)OH extract and its fractions, administered orally at the doses of 150 and 300 mg/kg, exhibited protective effect of at least 30% on the pain induced by acetic acid. The CH(2)Cl(2) fraction at 300 mg/kg showed a maximal effect of 78.49%. The CH(2)Cl(2)/CH(3)OH extract and its CH(2)Cl(2) fraction at the doses of 150 and 300 mg/kg significantly reduced the first phase of pain induced by formalin while the second phase was completely inhibited. The CH(2)Cl(2) fraction produced more than 45% reduction in the sensitivity to pain induced by pressure. The CH(2)Cl(2)/CH(3)OH extract of Kalanchoe crenata significantly increased the latency period in seizures induced by PTZ and significantly reduced the duration of seizures induced by the three convulsant agents. The extract protected 20% of animals against death in seizures induced by TSC and STN. These results suggest a peripheral and central analgesic activities as well as an anticonvulsant effect of the leaves of Kalanchoe crenata.

In vivo anti-nociceptive and anti-inflammatory effect of the two triterpenes, ursolic acid and 23-hydroxyursolic acid, from Cussonia bancoensis

Triterpenoids, ursolic acid (1) and 23-hydroxyursolic acid (2) were obtained from the hydrolysis of BuOH fraction of Cussonia bancoensis extract to test antinociceptive and anti-inflammatory effect of C. bancoensis (Araliaceae). Compound 1 and 2 exhibited anti-nociceptive effects, which were determined by acetic acid-induced writhing test and hot plate test. The effect of 2 was much more potent in acetic acid-induced writhing test than in hot plate test. Compound 1 and 2 significantly inhibited 1%-carrageenan-induced edema in the rat. These results suggest that the two triterpenes, ursolic acid and 23-hydroxyursolic acid, are responsible for the anti-nociceptive and anti-inflammatory effect of C. bancoesnsis.

Quinovic acid glycosides from Mitragyna stipulosa--first examples of natural inhibitors of snake venom phosphodiesterase I

Phytochemical investigations on the non-alkaloidal extracts of Mitragyna stipulosa bark has led to the isolation of a series of triterpenoids mainly consisting of quinovic acid ([structure: see text]) and its glycoside derivatives [structure: see text] and [structure: see text]. The other constituents isolated include alpha-amyrin, 3beta-acetyl ursolic acid and a mixture of oleanolic and ursolic acid and beta-sitosterol glucopyranoside. Their structures were identified by spectral and chemical studies and compounds [structure: see text] and [structure: see text] were, respectively, identified as quinovic acid 3-O-[beta-D-glucopyranoside] (quinovin glycoside C) and quinovic acid 3-O-[beta-D-quinovopyranoside]-27-O-[beta-D-glucopyranosyl] ester. Compounds [structure: see text] and [structure: see text] showed significant inhibitory activity against snake venom phosphodiesterase I.

Structure-activity relationship of triterpenoids isolated from Mitragyna stipulosa on cytotoxicity

Chromatographic separation of the stem bark extract of Mitragyna stipulosa afforded triterpene derivatives ursolic acid (1), quinovic acid (2), quinivic acid 3-O-beta-D-glucopyranoside (3, quinovin glycoside C), quinovic acid 3-O-[(2-O-sulfo)-beta-D-quinovopyranoside] (4, zygophyloside D) and quinovic acid 3-O-beta-D-quinovopyranosyl-27-O-beta-D-glucopyranosyl ester (5, zygophyloside B). These five compounds were subjected to the cytotoxicity on MTT assay system. Compound 1 among tested showed the most potent cytotoxicity. Quinovic acid showed less potent cytotoxicity than ursolic acid and sugar linkages to 2 decreased the cytotoxicity. Compound 4 more potent than 3 with indicate that the sulfonyl group significantly enhances the activity. This indicates that the glycosidic linkage in ursane-type triterpenoids has mainly negative effect on cytotoxicity unlike in oleanane-type glycosides.

Effect of essential oils from leaves of Ageratum conyzoides, Lantana camara and Chromolaena odorata on the mortality of Sitophilus zeamais (Coleoptera, Curculionidae)

Ageratum conyzoides, Chromolaena odorata, and Lantana camara, are common weed species in Cameroon. Essential oil extracts from their leaves were tested for efficacy on the morality of the maize grain weevil, Sitophilus zeamais (Coleoptera, Curculionidae). Concentrations of the essential oils relative to the maize grains of 0.013, 0.025, 0.05 and 0.1% (v/w) were used for A. conyzoides and 0.063, 0.125, 0.25 and 0.50% (v/w) for C. odorata and L. camara. Twenty 7-day old adult weevils were fed on maize grains treated with the above concentrations of the essential oils in Petri dishes. Control dishes contained insects and maize grains without essential oils. The experiment was repeated three times. Dishes were incubated in the laboratory for 7 days at 26 degrees C and 75-85% relative humidity. Insect mortality was recorded every 24 h. Graphs of percentage mortality versus the duration of exposure were constructed and the LD(50) was computed for each oil. Significant insect mortality was obtained with all the essential oils used. The mortality of S. zeamais increased with the concentration of the essential oils of the three plants and the duration of exposure of the weevils on the treated substrates. The essential oil extract of Ageratum conyzoides was the most effective insecticide (LD(50)=0.09% in 24 h), followed by that of L. camara (LD(50)=0.16%) and C. odorata (LD(50)=6.78%). These results show that the essential oils of the leaves of some of these weed species may be exploited for insect control in stored products.