Hugh T. W. Tan

Cancer chemopreventive agents, 4-phenylcoumarins from Calophyllum inophyllum

In a search for anti-tumor-promoting agents, we carried out a primary screening of ten 4-phenylcoumarins isolated from Calophyllum inophyllum L. (Guttiferae), by examining their possible inhibitory effects on Epstein--Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. All of the compounds tested in this study showed inhibitory activity against EBV, without showing any cytotoxicity. Calocoumarin-A (5) showed more potent activity than any of the other compounds tested. Furthermore, calocoumarin-A (5) exhibited a marked inhibitory effect on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. The results of the present investigation indicate that some of these 4-phenylcoumarins might be valuable as potential cancer chemopreventive agents (anti-tumor-promoters).

Cancer chemopreventive activity of naphthoquinones and their analogs from Avicennia plants

As a part of screening studies for cancer chemopreventive agents (anti-tumor promoters), six natural and four synthetic naphthoquinones and five of their analogs were tested for their inhibitory activities against Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. Some of the 1,4-naphthoquinones and their analogs were found to show remarkably potent activities, without showing any cytotoxicity. 1,4-Furanonaphthoquinone (5) and its analog (9) isolated from Avicennia plants (Avicenniaceae), having an alcoholic OH group on the dihydrofuran-ring, displayed the most potent activity. Furthermore, avicenol-A (9) exhibited a marked inhibitory effect on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. The result of the present investigation indicated that some of these 1,4-naphthoquinones and their analogs might be valuable as potent cancer chemopreventive agents.

Evaluation of the allergenicity of tropical pollen and airborne spores in Singapore

Background: Sensitization to pollen and spores of the Southeast Asian tropical region is not well documented. This study evaluated the allergenicity of the tropical airspora in Singapore.

Economic and environmental impacts of harmful non-indigenous species in Southeast Asia.

Harmful non-indigenous species (NIS) impose great economic and environmental impacts globally, but little is known about their impacts in Southeast Asia. Lack of knowledge of the magnitude of the problem hinders the allocation of appropriate resources for NIS prevention and management. We used benefit-cost analysis embedded in a Monte-Carlo simulation model and analysed economic and environmental impacts of NIS in the region to estimate the total burden of NIS in Southeast Asia. The total annual loss caused by NIS to agriculture, human health and the environment in Southeast Asia is estimated to be US

Adinandra belukar: an anthropogenic heath forest in Singapore

33.5 billion (5th and 95th percentile US

The biofuel potential of municipal solid waste

25.8–39.8 billion). Losses and costs to the agricultural sector are estimated to be nearly 90% of the total (US

Random amplified polymorphic DNA analysis of the moth orchids, Phalaenopsis (Epidendroideae: Orchidaceae)

23.4–33.9 billion), while the annual costs associated with human health and the environment are US

Xylem of rattans: vessel dimensions in climbing palms

1.85 billion (US

The extent of undiscovered species in Southeast Asia

1.4–2.5 billion) and US

Variations in tropical airspora in Singapore

2.1 billion (US