A TRITERPENOID COMPOUND FROM THE STEMBARK OF Aglaia argentea ( MELIACEAE )

A triterpenoid compound, 3-epicabraleahydroxylactone (1) has been isolated from the n-hexane extract of the stembark Aglaia argentea. The chemical structure of compound 1 was identified based on spectroscopic data and by comparison with the spectral data previously reported. A triterpenoid, 3-epicabraleahydroxylactone (1), was reported from this plant for the first time.


Plant Material
The stembark of A. argentea were collected in Bogor Botanical Garden, Bogor, West Java Province, Indonesia in January 2016.The plant was identified by the staff of the Bogoriense Herbarium, Research Center for Biology, Indonesian Institute of Science, Bogor, Indonesia and a voucher specimen (No.Bo-1288718) has been deposited at the herbarium.

General Experimental Procedure
Melting points were measured on an electrothermal melting point apparatus and are uncorrected.Added of UV Spectra were measured by using a TECAN Infinite M200 pro with MeOH.The IR spectra were recorded on a Perkin-Elmer spectrum-100 FT-IR in KBr.Mass spectra were obtained with a Synapt G2 mass spectrometer instrument. 1 H, 13 C, DEPT NMR spectral data and 1 H-1 H COSY, HMQC and HMBC experiments were performed on a JEOL ECZ-600 spectrometer at 600 MHz with CDCl 3 as a solvent, chemical shifts are given on a  (ppm) scale and tetramethylsilane (TMS) as an internal standard.Column chromatography was conducted on silica gel 60.TLC plates were precoated with silica gel GF 254 (Merck, 0.25 mm) and detection was achieved by spraying with 10% H 2 SO 4 in EtOH, followed by heating.

Extraction and isolation
The crushed and dried bark (2.5 kg) of A. argentea was extracted with methanol (14 L) at room temperature for 5 days.The methanol extract was evaporated under reduce pressure to give a brown residue (140 g g).The brown residue was first dissoved in H 2 O and then partitioned successively with n-hexane (3 L), EtOAc (3 L) and n-butanol (3 L).The n-hexane soluble fraction (14.1 g) was fractionated by vacuum liquid chromatography on silica gel using a gradient nhexane-EtOAc to give ten fractions (A-J).Fraction D (340 mg) was column chromatographed on silica gel, eluted with n-hexane:EtOAc (1:1), to give six subfractions (D01-D06).Subfraction D05 was column chromatographed on octa desyl silane, eluted with MeOH:MeCN:H 2 O (6:1:3) to give 1 (20.6 mg).

RESULTS AND DISCUSSION
The phytochemical test for the n-hexane extract showed the presence of triterpenoids.By using triterpenoid test to guide separations, the nhexane fraction was separated by column chromatography over silica gel by gradient elution.The fractions were repeatedly subjected to normalphase column chromatography and preparative TLC on silica gel GF 254 yielded a triterpenoud, 1 (Figure 1).
Compound 1, was obtained as white crystals.The molecular formula was established to be C 27 H 44 O 3 based on The HR-TOFMS spectrum m/z 417.3105 [M+H] + , calcld.for C 27 H 44 O 3 m/z 416.3290 together with NMR data (Tabel 1), thus requring six degrees of unsaturation.The UV spectrum showed no a conjugated double based on the absorption maximum above 20 nm.IR spectrum of 1 showed the presence of a hydroxyl group (3477 cm -1 ), aliphatic bands (2942 and 2860 cm -1 ), a carbonyl lactone (1715 cm -1 ), a gemdimethyl (1471 and 1387 cm -1 ) and an ether (1075 cm -1 ).
In order to clarify the position of functional group in compound 1, 1 H-1 H COSY and HMBC experiments were carried out and the results was shown in Figure 2. The 1 H-1 H COSY spectrum of 1 showed correlations in H 1 -H 2 -H 3 , H 5 -H 6 -H 7 , H 9 -H 11 -H 12 -H 13 , H 15 -H 16 -H 17 , and H 22 -H 23 , supporting the presence of a trisnortriterpenoid dammaran structure in 1.In the HMBC spectrum, the correlations arising from the tertiary methyl protons to their neighboring carbons enabled the assignment of the five singlet methyls at C-4 (2), C-10, C-8, C-14 and C-20, respectively.Methylenes protons at  H 1.40 and 1.56 were correlated to an oxygenated carbon at  C 76.3 (C-3), whereas one of a gem-dimethyl was correlated to an oxygenated carbon at C-3 ( C 76.3), indicated that a secondary hydroxyl group was attached at C-3.A methylene protons at  H 2.52 and 2.62 were correlated to carbonyl lactone at  C 176.9 (C-24), whereas the methyl proton at  H 1.33 was correlated to oxygenated carbon at C-20 ( C 90.3) and C-17 ( C 49.5), indicated that a lactone ring was attached at C-17.Consequently compound 1 was identified as a 3epicabraleahydroxylactone, and was reported from this plant for the first time.

CONCLUSION
A trisnortriterpenoid dammaran, 3epicabraleahydroxylactone (1) has been isolated from the n-hexane extract of the stembark Aglaia argentea.This investigation support the occurances of triterpenoid compounds in the Aglaia genus.

Table 1 .
NMR Data for Compound 1 (500 MHz for 1 H and 125 MHz for 13 C in CDCl 3 ) ACKNOWNLEDMENT This investigation was financially supported by Directorate General of Higher Education, Ministry of Research, Technology and Higher Education, Indonesia (Postgraduate Grant, 2015-206 by Unang Supratman).