INTRODUCTION:

Bauhinia purpurea linn.¹ (Fabaceae) is a flowering plant native to South China and southeastern Asia. In the United States of America, the tree grows in Hawaii, coastal California, southern Texas, and southwest Florida. Common names include Hong Kong Orchid Tree, Purple camel's foot, and Hawaiian orchid tree. It is a small to medium-sized deciduous tree growing to 17 m tall ^2-4. The investigation of chemical constituents of plants of the Fabaceae family has aroused considerable attention on account of the antitumor activities found in dibenzoxepins named bauhiniastatins 1-4 triterpenes isolated from plants of that family ⁵. In previous papers we described the chemical constitution of the isolated two new dimeric flavonoids from 70% aq. Acetone extract of B. purpurea leaves and phytol fatty esters, lutein, and β-sitosterol with Antifungal activity ⁶.The decoction the bark is recommended a useful wash in ulcers ⁷.During our continued investigation of this species, one new oleanane derivative has been isolated along with an extensive range of triterpene. Thus, in this paper we present the identification of α- amyrin caprylate and structural elucidation of a ester of triterpene, all triterpenes were isolated from the petroleum ether fraction of ethanolic extract (95%) of the leaf of Bauhinia purpurea.

METHODS:

General experimental procedure

All the melting points were recorded in a Toshniwal melting point apparatus and were uncorrected. IR spectra of the compounds were recorded using the KBr pellet method on a Perkin – Elmer model 700 IR spectrophotometer. ¹HNMR spectra of the compound were taken on Bruker Avance II 400 (400MHz) NMR spectrometer using CDCl₃as solvent. ¹³CNMR was recorded on Bruker Avance instrument with as CDCl₃ the solvent at 100.62 MHz. Mass spectra were taken on a LCMS-2010A APCI/ESI – MS (positive mode). ). TLC was carried out using Si– gel (Merck). Column chromatography was carried out on neutral alumina (S.D. fine chemicals Pvt. Ltd., Bombay, 70-300 mesh).

Collection of Plant material:

The leaves of Bauhinia purpurea were collected from Paneer, Deralakatte, Karnataka, India during Feb-March 2008 and its botanical identity was confirmed by Dr. Noeline J. Pintod Head of Botany Department St. Agnes College, Mangalore. A voucher specimen has been deposited in Department of Pharmacognosy, NGSMIPS, Mangalore.

Extraction and Isolation:

The shade dried powdered leaves (5 kg) were extracted in soxhlet apparatus with ethanol (95%). The ethanol was evaporated under reduced pressure to dry and then the extract (350g) was extracted with petroleum ether (60 – 80°C), ethyl acetate and chloroform and yielded 80g, 60g and 50g. The petroleum ether fraction was chromatographed onto neutral alumina eluted with mixture of petroleum ether -chloroform with increasing polarity to give 40 fractions. Fractions 3-9 were crystallized with MeOH give α- amyrin caprylate.

α- amyrin caprylate

All the isolated were identified by comparison of spectroscopic and physical data with the value reported in the literature ^8-10.

CHARACTERIZATION OF COMPOUND (1):

Compound (1) was obtained as white crystal (MeOH). mp. 160° , R_f : 0.82 (Petroleum ether: Chloroform, 90:10) .IR (KBr, cm ^-1): 2917.9( C-H str. in CH₃),2847.7 ( C-H str. in CH₂),1724.1 ( C=O str.), 1465.2(C-H def. in CH₃), 1377.2( C-H deformation in gem dimethyl),723.6 ( =C-H out plane bending);¹H-NNMR (CDCl₃, δ ppm) 5.34 (s, 1H, H-12, vinylic proton),3.73 ( s ,1H, H-3)0.89 (s,6H, CH₃-29 and CH₃-30), 1.20 (s,6H,CH₃-23 and CH₃-24), 1.04(s, 9H, 3XCH_3,CH₃-25, CH₃-26 and CH₃-28),1.30 (s,3H, CH₃-27),1.39 to 2.09 (s, 5H, 5XCH), 1.09 to 2.05 (m,18H, 9XCH₂),0.88 (s,3H, CH₃-8'), 1.2 to 1.72 ( m,10H, CH₂-3' to CH₂-7'),2.1 (s,2H, CH₂-2');¹³CNMR (CDCl₃)d: 37.44( C – 1), 28.26( C – 2), 77.35( C – 3), 37.44( C – 4), 56.05( C – 5),19.04( C – 6), 33.94( C – 7), 39.78( C – 8), 45.83( C – 9,17), d 36.51( C – 10), 23.09( C – 11,), d121.73 ( C – 12), 144.76 ( C – 13), 42.3 ( C – 14,19),31.65 ( C – 15), 26.05 ( C – 16,27), 39.88 ( C – 18), 37.37 ( C – 20), 32.81 ( C – 21), 28.26 ( C – 22), 23.06 ( C – 23, 24), 16.20 ( C – 25), 18.79 ( C – 26), 26 ( C – 27), 16.2 ( C – 28), 21.23 ( C – 29), 26.06(C-30), 173.33 ( C '-1), 33.94 ( C '-2), 29.72 ( C '-3- C '-5), 31.91 ( C '-6),22.17 ( C '-7), 14.1 ( C '-8). LC-MS positive mode m/z=552(M⁺, C₃₈H₆₄O₂), 537, 506, 445, 408(M⁺-144), 333, 324 (100%), 310, 254, 218, 190, 144.

RESULT AND DISCUSSION:

The phytochemical investigation of petroleum ether extract of leaf of Bauhinia purpurea afforded six triterpenoids and all these triterpenoids have been isolated first time from this plant Compound I (α- amyrin caprylate ) gave a characteristic colour reaction for triterpenes. The mass fragmentation was typically that of a -amyrin skeleton. An ester linkage was discernible from the characteristic IR adsorption at 1724.1 cm^-1. The -CH₂COO- of the ester was indicated by the characteristic singlet at d 2.35. Furthermore mass fragment m/z 408 is suggestive of the loss of caprylic acid (144) from the molecular ion (M⁺) 552.

ACKNOWLEDGEMENTS:

The author are thankful to principal and management of NGSMIPS, Mangalore for providing necessary facilities and SAIF Punjab for providing IR and ¹HNMR and¹³CNMR and Quest, Bangalore for providing LC-MS.

REFERENCES:

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Received on 25.03.2009 Modified on 19.05.2009

Asian J. Research Chem. 2(4):Oct.-Dec. 2009 page 569-570