Chemical Constituents from Aegle marmelos

Aegle marmelos, commonly known as “Ma Toom” in Thai, belongs to the Rutaceae family. Several parts of this plant have been used by the local Thai people in folk medicines. For example, the infusion of dried unripe fruits has been used as antidiarrhea and antidysentery agents, the juice from crushed leaves has been used for the treatment of bronchitis, and the decoction of root barks has also been used as anti-malarial drug. In addition, young leaves are used as vegetable. The chemical investigation of the leaves of this plant has revealed the presence of a number of alkaloids and coumarins. In our continuing study on chemical constituents from Thai medicinal plants, we now report herein the isolation and structure elucidation of a rare natural product oxazoline derivative product (1) along with eight known compounds (2-9) (Figure 1) from the roots and twigs of A. marmelos.


Introduction
Aegle marmelos, commonly known as "Ma Toom" in Thai, belongs to the Rutaceae family.Several parts of this plant have been used by the local Thai people in folk medicines.For example, the infusion of dried unripe fruits has been used as antidiarrhea and antidysentery agents, the juice from crushed leaves has been used for the treatment of bronchitis, and the decoction of root barks has also been used as anti-malarial drug. 1 In addition, young leaves are used as vegetable.The chemical investigation of the leaves of this plant has revealed the presence of a number of alkaloids [2][3][4][5][6][7] and coumarins. 1,8,9n our continuing study on chemical constituents from Thai medicinal plants, we now report herein the isolation and structure elucidation of a rare natural product oxazoline derivative product (1) along with eight known compounds (2-9) (Figure 1) from the roots and twigs of A. marmelos.

General procedure
UV spectra were recorded with a Perkin-Elmer UV-Vis spectrophotometer.The IR spectra were recorded with a Perkin-Elmer FT-IR spectrophotometer.The with tetramethylsilane (TMS) as an internal reference.High resolution mass spectra were obtained using Bruker microTOF mass spectrometer.Dried flash column chromatography and column chromatography (CC) were carried out on silica gel 60 H (Merck, 5-40 μm) and silica gel 100 (Merck, 63-200 μm), respectively.Precoated plates of silica gel 60 F 254 were used for analytical purposes.

Plant material
The roots and twigs of A. marmelos were collected from Chiang Rai Province, northern part of Thailand, in December 2008.Botanical identification was achieved through comparison with a voucher specimen number QBG 33029 in the Herbarium Collection of Queen Sirikit Garden, Mae Rim District, Chiang Mai, Thailand.

Extraction and isolation
The roots (160 g) and the twigs (4.5 kg) of A. marmelos were extracted with dichloromethane (CH 2 Cl 2 ), over a period of 3 days, at room temperature, and evaporated under reduced pressure, to provide crude CH 2 Cl 2 extracts of roots (8.40 g) and twigs (15.34 g).

Antimalarial assay
Antimalarial activity was evaluated against the parasite Plasmodium falciparum (K 1 , mutidrug resistant), using the method of Trager and Jensen. 10Quantitative assessment of in vitro malarial activity was determined by means of the microculture radioisotope technique based on the method described by Desjardins et al. 11 The inhibitory concentration (IC 50 ) represented the concentration that caused 50% reduction in parasite growth which was indicated by the in vitro uptake of [ 3 H]-hypoxanthine by P. falciparum.The standard compound was dihydroartemisinin (IC 50 4.1 nmol L -1 ).