Mangiferin, 2-b b-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 m mg/ml or 13.74 m mM) 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.

Hypertension is a disease, which if left untreated affects all important organs of human body. It is known as silent killer as without showing significant symptoms, it may quietly lead to stroke, brain hemorrhage, cardiac disorders, renal failure and vision loss. Hypertension has affected 10-15% of global population and killed a large number of human race in every region of world. Drugs used for its treatment on one hand are very expensive and beyond the reach of a common man while on the other hand, side effects associated with these drugs restricted the people to use them. Hence development of a cost effective antihypertensive drug with minimum or no side effects from commonly available indigenous medicinal plants is highly required. Keeping this in view as well as blood pressure reducing property of Bombax ceiba present work describes the hypotensive evolution of its stem bark alongwith toxicology and histopathology of active fraction.Bombax ceiba (syn. Bombax malabaricum DC) commonly known as silk cotton tree is an important medicinal plant. 1,2)Earlier investigations led to the identification of a sesquiterpene lactone, a potent growth inhibitor in fungi 3) and a flavonol glycoside possessing significant hypotensive and hypoglycaemic activities.4) Both of these compounds were isolated from roots and leaves of B. ceiba respectively. This is the first report of hypotensive evaluation of it's stem bark which has resulted in the isolation of a novel benzopyran dimer, shamimicin, lupeol 5) and fractions possessing hypotensive activity. In addition to this, methanolic extracts of different parts of plant, including flowers, pulp, stem and stem bark have also been studied for their effect on mean arterial blood pressure (MABP) of rats. MATERIALS AND METHODSInstrumentation Ultraviolet spectra were recorded in MeOH on Hitachi-U-3200 and infrared spectra were measured in CHCl 3 on JASCO-A-302 spectrophotometers. The electron impact (EI) mass spectra were recorded on a Finnigan MAT-112 instrument. Field desorption (FD-MS), fast atom bombardment (FAB-MS positive and negative) and exact mass measurements were carried out on a Finnigan MAT-312 instrument. High-resolution mass spectra were recorded on a JMS HX-110 spectrometer. The 1 H-and 13 C-NMR spectra were run in CDCl 3 on a Bruker Aspect AM-500 spectrometer operating at 500 MHz for A novel constituent, shamimicin, 1ٟ,1ٟ؆؆-bis-2-(3,4-dihydroxyphenyl)-3,4-dihydro-3,7-dihydroxy-5-O-xylopyranosyloxy-2H-1-benzopyran alongwith 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.

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.