Aglaia

Introduction

Within Meliaceae, Aglaia represents the largest genus comprising somewhat more than 100 species. The classification and ecology of the genus Aglaia have been investigated by Dr Caroline Pannell. Her monograph of the genus, published in 1992, represents an attempt to bring the genus into systematic order, to apply correct names and to recognise and name new species.
The genus Aglaia encompasses dioecious treelets and trees, occurring in the tropics and subtropics of South and Southeast Asia, from Sri Lanka and India, the most western distribution, to Australia and as far as the Polynesian island Samoa in the East.
Classification is based on morphological characters like the indumentum, flower characters and fruit dehiscence mechanisms, classifying this largest genus within the Meliaceae into more than 100 species. However, some taxonomic uncertainties still remain, due to considerable infraspecific variation of these morphological characters. Therefore, a significant taxonomic contribution is expected from phytochemical as well as molecular data.
Being a synthesis of the classification of the entire genus throughout its range, a broad species concept was adopted which left seven incompletely resolved 'complex species' and 28 'variable species'. The variation of the complex and variable species is best resolved at a regional level. This has been done for Borneo (Pannell 2004, Kew Bulletin 59: 87 - 94).
The results of phytochemical investigations and molecular systematic research further highlight variation within the complex species and may ultimately contribute to their resolution in whole or in part. Dried herbarium specimens and living plants of Aglaia can be determined, by the expert, from vegetative characters such as the structure and distribution of the stellate hairs and peltate scales, which often form a distinctive indumentum on the leaves, inflorescences and infructescences.
We relied for accurate naming of specimens from which we isolated chemical compounds, on determination of plant material by Dr Pannell and are much obliged to her qualified support.

Phytochemicals

Triterpenes are generally considered as main constituents, accompanied by significant amounts of sesquiterpenes. The chemistry of Aglaia has been and still is extensively investigated by phytochemists. Most attention has been directed towards flavaglines, typical benzofuran and benzopyran derivatives restricted exclusively to this genus. Flavaglines comprise cyclopenta[b]tetrahydrobenzofurans (rocaglamides), cyclopenta-[bc]benzopyrans (aglains, aglaforbesins, thapsakins) and benzo[b]oxepines (forbaglines, thapoxepines) (Bacher et al., 1999, Proksch et al., 2001). Together with typical bisamides , flavaglines represent distinct phytochemical characters restricted to the genus Aglaia (Brader et al., 1998). Moreover, different Aglaia species synthesize several derivatives of flavonoids and lignans .

Bioactivities - Why are we interested in Aglaia?

Benzofurans, unique structures of the genus Aglaia, were shown to possess high insecticidal properties (King et al. 1982, Janprasert et al., 1993, Molleyres and Kumar 1996, Brader et al. 1998). Moreover, pronounced cytotoxicity of several Aglaia species against different human tumor cell lines attracted woldwide attention, resulting in detailed investigations of cytotoxic derivatives and their mode of actions (King et al. 1982, Mata-Greenwood et al. 2001). Engelmeier et al., 2000, detected highly active fungicides against the rice blast disease, Pyricularia grisea, with the flavagline rocaglaol as most active derivative. Furthermore, platelet aggregation inhibitory effects (Ko et al. 1992), antiviral (Joshi et al. 1987), antibacterial (Kakrani and Nair 1982) and anthelmintic bioactivities (Nanda et al. 1987) were reported for these genus.

The chemical composition of Aglaia displays an excellent example for a link between basic research (e.g. chemosystematics, investigation of biogenetic capacities) and applied aspects (finding of new lead structures for application in sustainable agriculture and in medicinal research).

Literature

Bacher, M., Hofer, O., Brader, G., Vajrodaya, S., Greger, H., 1999. Thapsakins: possible biogenetic intermediates towards insecticidal cyclopenta[b]benzofurans from Aglaia edulis. Phytochemistry 52, 253-263.

Brader, G., Vajrodaya, S., Greger, H., Bacher, M., Kalchhauser, H., Hofer, O., 1998. Bisamides, lignans, triterpenes and insecticidal cyclopentabenzofurans from Aglaia species. J. Nat. Prod. 61, 1482-1490.

Engelmeier, D., Hadacek, F., Pacher, T., Vajrodaya, S., Greger, H. (2000): Cyclopenta[b]benzofurans from Aglaia species with pronounced antifungal activity against rice blast fungus (Pyricularia grisea). J. Agric. Food Chem. 48, 1400-1404.

Janprasert, J., Satasook, C., Sukumalanand, P., Champagne, D. E., Isman, M. B., Wiriyachitra, P., Towers, G. H. N. (1993): Rocaglamide, a natural benzofuran insecticide from Aglaia odorata. Phytochemistry 32, 67-69.

Joshi, M. N., Chowdhury, B. L., Vishnoi, S. P., Shoeb, A., Kapil, R. S. (1987): Antiviral activity of (+)-odorinol. Planta med. 53, 254-255.

Pannell, C.M., 1992. A Taxonomic Monograph of the genus Aglaia Lour. (Meliaceae). Kew Bulletin Additional Series XVI. Royal Botanic Gardens, Kew, London.

Proksch, P., Edrada, R.A., Ebel, R., Bohnenstengel, F.I., Nugroho, B.W., 2001. Chemistry and biological activity of rocaglamide derivatives and related compounds in Aglaia species (Meliaceae). Current Organic Chemistry 5, 923-938.

Kakrani, H. K., Nair, G. V. (1982): Antibacterial and antifungal activity of volatile oil from the seeds of Aglaia odoratissima. Fitoterapia 53, 107-109.

King, M. Lu, Chiang, C. C., Ling, H. C., Fujita, E., Ochiai, M., McPhail, A. T. (1982): X-ray crystal structure of rocaglamide, a novel antileukemic 1H-cyclopenta[b]benzofuran from Aglaia elliptifolia. J. Chem. Soc., Chem. Commun. 20, 1150-1.

Ko, F. N., Wu, T. S., Liou, M. J., Huang, T. F., Teng, C. M. (1992): PAF antagonism in vitro and in vivo by aglafoline from Aglaia elliptifolia Merr. Eur. J. Pharmacol. 218, 129-35.

Mata-Greenwood, E., Ito, A., Westenburg, H., Cui, B., Mehta, R. G., Kinghorn, A. D., Pezzuto, J. M. (2001): Discovery of novel inducers of cellular differentiation using HL-60 promyelocytic cells. Anticancer Res. 21, 1763-1770.

Molleyres, L. P., Kumar, V. (1996): Insecticidal polycyclic compounds. PCT Int. Appl. WO, 96/04284; CA 124, 335673.

Nanda, A., Iyengar, M. A., Narayan, C. S., Kulkarni, D. R. (1987): Investigations on the root bark of Aglaia odoratissima. Fitoterapia 58, 189-91.