Isolation and characterization of a steroidal compound from the hexane extract of the leaves of Artabotrys odoratissimus

Artabotrys odoratissimus has been investigated by many workers for its constituents. Previous phytochemical studies have revealed this genus to be rich in secondary metabolites including phenylcoumarins, xanthones and triterpenoids. So far, not many studies have been carried out on this genus but there are some reports on this plant. Our recent study on the hexane extract of the leaves of A. odoratissimus, have led to the isolation of steroidal compound. The structure of the compound has been established by modern spectroscopic techniques such as IR, H-NMR, CNMR and mass-spectroscopy and identified as tetracontan-15-one.


EXPERIMENTAL: GENERAL
Freshly distilled solvents were used for extraction, isolation and purification.Evaporations were performed under reduced pressure in a Buchii rotary evaporator.IR spectra were recorded (KBr discs) on a Shimadzu UV-168A Spectrophotometer, validation (Vmax in cm -1 ). 1 H-NMR were recorded on a Bruker R-32 (300 MHz) instrument in CDCl 3 and DMSO-d6 with TMS as an internal standard (Chemical Shifts in δ, ppm).All solvents used were of analytical grade.Thin-layer chromatography (TLC) was performed using Silica gel GF254.

Plant materials
The leaves of A. odoratissimus were collected from the gardens of Ujjain city and university campus and were identified by the authorities of IEMPS, Vikram University Ujjain (M.P) India.

Extraction of the Compound D1
Dried leaves of the plant (5 kg) were milled into powder and then extracted with hexane (8 L) in a Soxhlet extractor for 36 h.The extract was evaporated in a rotatory evaporator and dried by vacuum pump.The hexane extract (50 g) was suspended on water and extracted successively with hexane, hexane: Benzene, Benzene: Ethyl acetate and Ethyl acetate:Chloroform to yield hexane (15 g), Hexane: Benzene (5 g), Benzene:Ethylacetate (12 g), Ethylacetate:Chloroform (3.2 g), soluble fractions respectively.The hexane (15 g) soluble fraction was subjected to column chromatography was eluted initially with hexane, hexane: Benzene followed by the mixture of Benzene with increasing amount of ethyl acetate and finally with methanol.These elutes were collected in a series of test tubes with 15 ml in each fraction.Each fraction was examined by TLC.Based on the similar TLC behavior, these elutes were combined to yield D1, D2, D3, D4, D5, D6, D7, D8, D9 and D10.The fractions D1-D3 (that is, hexane fractions) were concentrated and allowed to stand at room temperature when a circular white amorphous crystal was obtained and this was marked as compound D1.The amorphous crystal was washed with methanol successively.The crystal dissolved in chloroform, applied in TLC micro-glass slide, and viewed in an iodine chamber were two different spots were detected.Therefore, the compound was needed further purification and dissolving in the mixture of CHCl 3 and methanol (10:1) and kept at room temperature.After 24 h a white amorphous crystal was precipitated out at the bottom of the conical flask.The crystallization process was repeated three times and finally white crystal (80 mg) were obtained.

RESULTS AND DISCUSSION
The TLC examination of the isolated compound from the hexane extract of the leaves of Artabotrys odoratissimus upon exposure to iodine vapour showed a bright single spot.The compound was obtained as white crystals (m.p=285°C).HRMS of compound D1 exhibited molecular ion at m/z 576, which is consistent with the molecular formula C 40 H 80 O.It was readily soluble in CHCl 3 .IR spectrum showed bands at 2919,2850,1735,1541,1463,1074,801,730 to 720 cm -1 suggesting aliphatic ketonic nature of the compound (Mehta et al., 1999;Bellamy, 1962).
The 1 H NMR spectrum showed triplet at δ 0.86 for six protons of terminal methyl groups.A triplet at δ 2.35 for alpha methylene (CH 2 OCH 2 ) protons to the carbonyl group.A broad singlet at δ 1.56 for beta methylene protons.A broad singlet at δ 1.26 assigned to rest of the methylene protons (Falch et al., 2004;Fauhl et al., 2000;Guillen and Ruiz, 2005;Guillen and Ruiz, 2003;Panico et al., 1994;Gunstone et al., 1975;Lie Ken Jie et al., 2003).C 13 NMR spectrum value were consistent with the proposed structure, it showed a peak at δ 173.8 for carbonyl carbon.The peaks at δ 35.5 and 31.9 attributed to the methylene carbons attached at alpha and beta positions of the carbonyl group.A bunch of peaks at δ 29.9-22.7 corresponds to the remaining methylene carbons.Peak at δ 15.5 correspond to the methyl carbons.
The EIMS showed the molecular ion peak at m/z 567 suggesting its molecular formula as C 40 H 80 O.The mass fragmentation was characteristic of long chain hydrocarbon.The separation of most of the peaks by 14 and 28 mass units and appearance of CnH 2 n+1 and CnH 2 n-1 ion series confirmed its long chain aliphatic nature.The fragment at m/z 240 formed by the Mc Lafferty rearrangement indicated the position of carbonyl group.Other abundant fragments at m/z504, 476, 462, 450, 435, 378, 182, 141 and 58 were characteristic of the long chain aliphatic ketone (Mehta et al., 1999;Gowarikar et al., 1997;Bellamy, 1962;Manorangani et al., 1999;Silverstein et al., 1984;Christie et al., 1993;Ali et al., 2001;Dobson and Sebedio, 1999;McLafferty, 1973).

Conclusion
The results of the present investigation showed the occurrence of Tetracontan-15-onetype compound in plant kingdom.The title Compound was isolated from this plant for the first time.