Pichaet Wiriyachitra

Rocaglamide, a natural benzofuran insecticide from Aglaia odorata

Abstract Rocaglamide, a highly substituted benzofuran, was isolated and identified as the active insecticidal constituent in the twigs of the Chinese rice flower bush, Aglaia odorata. This compound inhibits larval growth and is insecticidal to both variegated cutworms, Peridroma saucia and Asian armyworms, Spodoptera litura. LD50 values for fourth-instar P. saucia larvae were found to be 0.32 μg larvae−1 topically and 0.34 μg larvae−1 orally. Dammarane triterpenes and aminopyrrolidine bis-amides such as odorinol isolated from A. odorata were inactive against P. saucia.

A triterpenoid saponin from Maesa ramentacea

The structure of a piscicidal triterpenoid saponin (saponin A) isolated from the leaves of Maesa ramentacea has been shown to be 3-O-[[(alpha-rhamnopyranosyl (1-->2)-alpha-L-rhamnopyranosyl(1-->2)-beta-D-galactopyranosyl (1-->3)]-[beta-D-glucopyranosyl(1-->2)]-beta-D-glucuronopyranosyl] barringtogenol C21, 22-O-diangeloate. Extensive use was made of homo- and heteronuclear 2D NMR techniques.

Insecticidal bioactivity of crude extracts of Aglaia species (meliaceae)

Crude foliar extracts of 19 species of Aglaia (Meliaceae), mostly of Indo-Malaysian origin, were screened for larval growth inhibiting and insecticidal effects on the polyphagous lepidopteran Peridroma saucia (Noctuidea). Extracts of at least seven of these species significantly reduce larval growth of P. saucia. Aglaia odorata yielded the most inhibitory extracts, but there is significant (35-fold) geographical variation in the bioactivity of extracts within this widespread species. In addition, extracts of bark are significantly more active than foliar extracts. Foliar extracts significantly deter neonate larvae, but nutritional analyses of fourth instar larvae fed artificial diets laced with A. odorata extracts indicate that both diet consumption and dietary utilizatin are impaired. These results are similar to that obtained with pure (−)-rocaglamide, an insecticidal principle isolated from A. odorata. This species should provide a useful starting point for the development of a botanical insecticide.

Toxicity of the Thai piscicidal plant, Maesa ramentacea, to freshwater fishes in ponds

Abstract The Thai plant, Maesa ramentacea , and tea seed cake were tested as piscicides in earthen ponds at a concentration of 25 mg l −1 against five fish species i.e., Clarias sp., Cyprinus carpio , Gambusia sp., Oreochromis niloticus and Puntius gonionotus . The lowest mortality in 24 h in M. ramentacea (20% mortality) and tea seed cake (28% mortality) were found in Clarias sp. The highest mortality in 24 h in M. ramentacea (97% mortality) and tea seed cake (65% mortality) were found in P. gonionotus . The effectiveness of both piscicides in killing each test fish species was not significantly different. However, M. ramentacea was about 50% more effective than tea seed cake for the eradication of C. carpio and P. gonionotus in ponds. The toxicity persistence was not significantly different with respect to the piscicides and time. Fish seed can be released into rearing ponds 4 days after applying either piscicides.

Insecticidal activity of Aglaia odorata extract and the active principle, rocaglamide, to the European corn borer, Ostrinia nubilalis Hübn. (Lep., Pyralidae)

Abstract: A standardized twig extract of the Asian shrub, Aglaia odorata Lour. (Meliaceae), and rocaglamide, a purified active principle of the extract, were evaluated for potential to control the European corn borer (Ostrinia nubilalis Hübn.), via incorporation into meridic diet fed to larvae. Life cycle bioassays using the extract revealed that it inhibited larval growth at all concentrations tested (12.5–100 p.p.m./fresh wt.) and delayed mean time to pupation from 24.1 days (control) to 83.8 days (50 ppm). Other effects include reduced pupal and adult weights and an increase in the frequency of deformed pupae. Investigation of consumption rates and dietary utilization in larvae feeding on diet containing the extract suggested that it acts via a combination of antifeedant and postingestive (toxic) actions. Life cycle bioassays using rocaglamide demonstrated that this compound is an extremely potent inhibitor of larval growth, with concentration dependent activity observed at dietary concentrations from 0.05‐0.02 ppm. Effects at these levels include severe reductions in growth and pupal weight, and increases in larval mortality and time to pupation. Rocaglamide appears to be as, or even more active, than the very effective botanical pesticide azadrachtin from the neem tree.

Inhibition of fungal growth by an aqueous extract and saponins from leaves of Maesa ramentacea wall

An aqueous extract of Maesa ramentacea leaves and a mixture of saponins from the leaves were examined for their effect of hyphal growth. The extract and saponins inhibited growth of 10 fungal species which incite agriculturally important diseases in Thailand or Canada. The minimum inhibitory concentration (MIC) values for a significant inhibition of growth by 16 of the 18 fungal isolates tested were 50 μg ml−1 or less for the aqueous extract and 10 μg ml−1 or less for the saponin mixture. For the two least responsive isolates the MIC values for the aqueous extract were 500 μg ml−1 while those for the saponins were 50 or 10 μg ml−1. The range of MIC values for the more tropical Thai pathogens was lower than that for the Canadian fungi. The strong antifungal activity of the saponin mixture and their concentration in M. ramentacea leaves suggests that native levels of these compounds may be associated with inherent resistance to a spectrum of fungal pathogens.