New bioactive monoterpene indole alkaloid from Rinorea yaundensis Engl.

Extraction of the aerial part of Rinorea yaundensis has led to the isolation of a new monoterpene indole alkaloid (1) along with 10 known compounds (2-11) for the first time from this plant. Their structures were determined by HRMS and NMR spectroscopic analyses as yaundentine hydrochloride (1), Nb-oxide of iso-reserpiline (2), iso-reserpiline (3), iso-carapanaubine (4), lichenxanthone (5), stigmastane-3,6-dione (6), methyl ß-orcinol carboxylate (7), ß-sitosterol-3-O-ß-D-glucoside (8), betulinic acid (9), ursolic acid (10) and benzoic acid (11) while the stereochemistry and absolute configuration of 1 was confirmed by single crystal x-ray crystallography and circular dichroism CD spectrum. Yaundentine hydrochloride (1) exhibited pronounced antioxidant, urease and lipoxygenase inhibitory activities with IC50 values of 35.6 ± 0.23, 20.3 ± 0.58 and 29.6 ± 0.77 µM, respectively. Compound 1 also showed good antimicrobial activity against some Gram positive and negative bacteria.

Shamiminol: a new aromatic glycoside from the stem bark of Bombax ceiba.

A new aromatic glycoside, shamiminol was isolated from the stem bark of Bombax ceiba along with the known constituents stigmasta-3,5-diene, lupenone, (+/-)-lyoniresinol 2a-O-beta-D-glucopyranoside and opuntiol, obtained for the first time from this plant. The structure of shamiminol was elucidated on the basis of extensive 1D- and 2D-NMR spectroscopic and mass spectrometric studies as 3,4,5-trimethoxyphenol 1-O-beta-D-xylopyranosyl-(1 --> 2)-beta-D-glucopyranoside (1).

Temperature and solvent dependent NMR studies on mangiferin and complete NMR spectral assignments of its acyl and methyl derivatives.

By employing concerted 1 and 2D NMR techniques, exact NMR spectral assignments have been made of the acyl (2-7) and methyl (8 and 9) derivatives of mangiferin (1) isolated from the leaves of Bombax ceiba. Derivatives 2, 8 and 9 have been reported in literature, while 3-7 represent new compounds. The acetates 2 and 3 were found to be unstable and were converted into the same penta-acetate 4 at room temperature. Extensive NMR studies on mangiferin (1) and its derivatives showed that H-4 exchanges with deuterium of the solvent molecule more easily. This exchange under acidic conditions occurred at that position (C-4) where electrophilic substitution reactions can easily take place. This is the first report describing the exchange of C-4 proton of mangiferin (1), or any other xanthone, with deuterium of solvent molecules.

Analgesic and antioxidant activity of mangiferin and its derivatives: the structure activity relationship.

Mangiferin, 2-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxy-9H-xanthen-9-one, obtained directly from methanolic extracts of Bombax ceiba leaves in substantial amounts demonstrated strong antioxidant activity (EC(50) 5.8+/-0.96 mug/ml or 13.74 muM) using DPPH assay comparable to rutin, commonly used as antioxidant for medical purposes. The acetyl and cinnamoyl derivatives were found to be less active than mangiferin whereas, methyl and 3,6,7-trimethylether tetraacetate derivatives were inactive implying that for antioxidant activity, free hydroxyl groups and catechol moiety are essential. Moreover, mangiferin showed hepatoprotective activity against carbon tetrachloride induced liver injury further supporting the free radical scavenging property in the in vivo system. Additionally, plant extracts and mangiferin failed to exhibit acute anti-inflammatory activity whereas, it displayed significant analgesic effect in acetic acid-induced writhing and hot plate tests in mice. Using naloxone, it was revealed that plant extracts induced analgesia was independent of opioid receptor, whereas, mangiferin demonstrated significant interaction with it at peripheral site with a slight contribution at the neuronal level.

Hypotensive activity and toxicology of constituents from Bombax ceiba stem bark.

A novel constituent, shamimicin, 1"', 1"""'-bis-2-(3,4-dihydroxyphenyl)-3,4-dihydro-3,7-dihydroxy-5-O-xylopyranosyloxy-2H-1-benzopyran along with lupeol, which possesses potent hypotensive activity, has been isolated from Bombax ceiba stem bark. BCBMM--one of the most active hypotensive fractions has revealed its adverse effects on heart, liver and kidneys of mice at the dose of 1000 mg/kg/d.