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Hydnocarpus wightiana is advocated in traditional Indian medicine to possess strong antidiabetic activity. In the course of identifying bioactive fractions from Indian medicinal plants we observed that acetone extract of the seed hulls of H. wightiana possess strong free radicals (DPPH and ABTS) scavenging, alpha-glucosidase and moderate N-acetyl-beta-D-glucosaminidase inhibitory activities. Further fractionation of the extract led to the isolation of hydnocarpin, luteolin and isohydnocarpin in substantial yields. All the compounds showed strong ABTS scavenging property. However, only luteolin could display strong DPPH scavenging activity. Furthermore, all the three compounds also showed varying degrees of alpha-glucosidase and N-acetyl-beta-D-glucosaminidase inhibitory activity, luteolin being the superior. The kinetics of alpha-glucosidase inhibition by these compounds showed that acetone extract inhibits the enzyme in competitive manner however, luteolin and isohydnocarpin showed mixed-type inhibition. This is the first report assigning hydnocarpin and isohydnocarpin free radical scavenging, alpha-glucosidase and N-acetyl-beta-D-glucosaminidase inhibitory properties and luteolin as N-acetyl-beta-D-glucosaminidase inhibitor. This study suggests that presence of amphiphilic antioxidant molecules along with enzyme inhibitory activities in the acetone extract of H. wightiana seed hulls may be responsible for the antidiabetic properties as advocated in traditional medicine.

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Bioassay-guided fractionation of different extracts of both stem and stem bark of Stereospermum personatum led to the isolation of free-radical-scavenging and xanthine oxidase inhibitory molecules along with three new anthraquinones, sterequinones F-H (1-3), a new naphthoquinone, sterequinone I (4), two new phenethyl esters, 2(4'-hydroxyphenyl)ethyl undecanoate (14) and 2(4'-hydroxyphenyl)ethyl nonacosanoate (15), and a new 3,4,5-trimethoxycinnamyl ether, 2-methoxy-4-[3'-(3'',4'',5''trimethoxyphenyl)allyloxymethyl]phenol (16), together with known compounds. The antioxidant and xanthine oxidase inhibitory potentials of the isolated compounds are reported.

Deoxygenation of aromatic and aliphatic amine N-oxides to the corresponding amines is achieved under mild conditions. The reagent combination employed for this transformation is polymethylhydrosiloxane (PMHS) in the presence of either tetrakis (triphenylphosphine) palladium (0) [Pd(PPh 3 ) 4 ], titanium (IV) isopropoxide [Ti(i-PrO) 4 ] or palladium on carbon (Pd/C).Amine N-oxides have attracted the attention of synthetic organic chemists due to their differential chemical behavior as compared to their parent amines. It is well documented that hetero aromatic amine N-oxides behave differently in regioselectivity. 2 Thus oxidation of amines to amine N-oxides and reverting back to the parent amine constitutes a useful transformation set (Scheme). This latter transformation is complex for which several reagents have been developed. Aromatic N-oxides are relatively more stable than aliphatic ones and are resistant to deoxygenation, 3 although some of them undergo deoxygenation with sulfurous acid. 4 Traditionally deoxygenation has been carried out with complex hydrides, 5 trivalent phosphorus compounds, 6 various sulfur and selenium compounds, 7 dissolved metals, 8 iron, 9 titanium trichloride in aqueous solution, 10 titanium tetrachloride in the presence of zinc or magnesium 11 or catalytic hydrogenation. 12 These deoxygenations however require relatively drastic reaction conditions. Some of the reagents used for selective deoxygenation include trialkyl amine-sulfur dioxide complexes, 13 aluminium iodide, 14 acetic formic anhydride, 15 ammonium formate-palladium on carbon, 16 sodium hydrogen telluride, 17 chromium(II)chloride, 18 low valent titanium, 19 sodium borohydride 20 and SmI 2 . 21 Recently titanocene methylidene complex derived from Tebbe and Petasis reagent, 22 triphenyl phosphene-oxorhenium (V) catalyst, 23 In/aq. NH 4 Cl, 24 and Zn/aq. NH 4 Cl 25 mediated deoxygenations of amine N-oxides have been reported. Some of these are associated with limitations regarding selectivity and/or incompatibility with other functional groups and are expensive, hazardous and/or sensitive to both air and moisture. We have been exploring the utility of polymethylhydrosiloxane (PMHS) as an efficient reduction reagent 26 besides others. 27 It was expected that the N-oxide class of compounds would also reduce back to parent amines in presence of PMHS based on the literature precedence. 12,16 To make this expectation a reality, the easily accessible pyridine N-oxide 1a (entry 1, Table 1) was subjected to polymethylhydrosiloxane in the presence of Pd/C activator and formation of pyridine 2a was observed in 90% yield. However the combination was not selective for substrates containing olefin, nitro and other reducible groups. Thus several catalysts were tested for activating PMHS which is otherwise inert and we found titanium (IV) isopropoxide [Ti(i-PrO) 4 ] and tetrakis (triphenylphosphine) palladium (0) [Pd(PPh 3 ) 4 ] are also to be very useful ones. Accordingly, the same pyridine N-oxide 1a was subjected to PMHS in presence ...