Soedarsono Riswan

Soils on exposed Sunda Shelf shaped biogeographic patterns in the equatorial forests of Southeast Asia

The marked biogeographic difference between western (Malay Peninsula and Sumatra) and eastern (Borneo) Sundaland is surprising given the long time that these areas have formed a single landmass. A dispersal barrier in the form of a dry savanna corridor during glacial maxima has been proposed to explain this disparity. However, the short duration of these dry savanna conditions make it an unlikely sole cause for the biogeographic pattern. An additional explanation might be related to the coarse sandy soils of central Sundaland. To test these two nonexclusive hypotheses, we performed a floristic cluster analysis based on 111 tree inventories from Peninsular Malaysia, Sumatra, and Borneo. We then identified the indicator genera for clusters that crossed the central Sundaland biogeographic boundary and those that did not cross and tested whether drought and coarse-soil tolerance of the indicator genera differed between them. We found 11 terminal floristic clusters, 10 occurring in Borneo, 5 in Sumatra, and 3 in Peninsular Malaysia. Indicator taxa of clusters that occurred across Sundaland had significantly higher coarse-soil tolerance than did those from clusters that occurred east or west of central Sundaland. For drought tolerance, no such pattern was detected. These results strongly suggest that exposed sandy sea-bed soils acted as a dispersal barrier in central Sundaland. However, we could not confirm the presence of a savanna corridor. This finding makes it clear that proposed biogeographic explanations for plant and animal distributions within Sundaland, including possible migration routes for early humans, need to be reevaluated.

Potential Anticancer Activity of Naturally Occurring and Semisynthetic Derivatives of Aculeatins A and B from Amomum aculeatum

Activity-guided fractionation of hexanes- and CHCl 3-soluble extracts of Amomum aculeatum leaves, collected in Indonesia, led to the isolation of three new dioxadispiroketal-type ( 3- 5) and two new oxaspiroketal-type ( 6 and 7) derivatives. Nine semisynthetic derivatives ( 1a- 1h and 2a) of the parent compounds, aculeatins A ( 1) and B ( 2), were prepared. All isolates and semisynthetic compounds were tested against a small panel of human cell lines. Of these, aculeatin A ( 1; ED 50 0.2-1.0 microM) was found to be among the most cytotoxic of the compounds tested and was further evaluated in an in vivo hollow fiber assay; it was found to be active against MCF-7 (human breast cancer) cells implanted intraperitoneally at doses of 6.25, 12.5, 25, and 50 mg/kg. However, when 1 was tested using P388 lymphocytic leukemia and human A2780 ovarian carcinoma in vivo models, it was deemed to be inactive at the doses used.

Bioactive constituents of the stem bark of Mitrephora glabra

Bioactivity-guided fractionation of the stem bark of Mitrephora glabra yielded nine compounds, comprising three ent-kaurenoids (1-3), five polyacetylenic acids/esters (4-8), and one aporphine alkaloid, liriodenine (9). The structures of the six new compounds (1-3, 5, 7, and 8) were determined by spectroscopic data interpretation. All compounds were evaluated for their inhibitory activities against a panel of cancer cell lines and a battery of microorganisms.

The estimation of temporal processes in tropical rain forest: a study of primary mixed dipterocarp forest in Indonesia

In the absence of growth rings it is difficult to give a precise time scale for pro- cesses associated with the re-establishment of tropical rain forest. This paper explores other methods by which a time scale may be constructed. The proportions of primary and secondary species, an index of similarity, biomass measurements, girth dimensions and gap size are all considered from sites in East Kalimantan, Indonesia. Data from primary, secondary and experi- mentally cleared forest sites are compared to estimate the minimum time required for various phases involved in the re-establishment of tropical rain forest after disturbance. A simple model is proposed to accommodate the data and other estimates in the literature. The model predicts a minimum period for the stablization of secondary species numbers as 60-70 years and the replacement of primary species as 150 years at which point gap formation is initiated. After approximately 220-250 years biomass stabilizes while individual trees exist for over 500 years.

Cytotoxic triterpenes from the twigs of Celtis philippinensis.

Two triterpene esters, 3beta-trans-sinapoyloxylup-20(29)-en-28-ol (1) and 3beta-trans-feruloyloxy-16 beta-hydroxylup-20(29)-ene (2), were isolated as cytotoxic constituents from the chloroform-soluble extract of the twigs of Celtis philippinensis, along with five known triterpenes, 3beta-O-(E)-feruloylbetulin (3), 3beta-O-(E)-coumaroylbetulin (4), betulin (5), 20-epibryonolic acid (6), and ursolic acid (7). The structures of 1 and 2 were assigned from their 1D and 2D NMR spectroscopic data. All isolates were evaluated for cytotoxicity against several human cancer cell lines.

Three xanthones from Poeciloneuron pauciflorum and Mammea acuminata

Abstract From the stem of Poeciloneuron pauciflorum , two new xanthones (1,6-dihydroxy-7-methoxyxanthone and 1,6-dihydroxy-7-methoxyxanthone 6-O-β- d -glucoside ) in addition to 12 known compounds (1,5-dihydroxy-, 1,5-dihydroxy-3-methoxy-, 1,7-dihydroxy-, 1-hydroxy-7-methoxy-, 2-methoxy-, 4-methoxy-, 1,4,5-trihydroxy-, 1,3,5-trihydroxy-, 1,3,6-trihydroxy-7-methoxy-, 1,3,7-trihydroxy-, 3-hydroxy-2-methoxyxanthone and (−)-epicatechin) were isolated. From the aerial parts (stems and bark) of Mammea acuminata , a new xanthone (2,7-dihydroxyxanthone) was isolated in addition to two known xanthones (1,5-dihydroxy- and 5-hydroxy-1-methoxyxanthone) and (−)-epicatechin. The structures were established by spectral analysis and total synthesis in case of 1,6-dihydroxy-7-methoxyxanthone.

Bioactivity-guided isolation of cytotoxic sesquiterpenes of Rolandra fruticosa

Cytotoxicity-guided fractionation of a methanol extract of the leaves and twigs of Rolandra fruticosa using the HT-29 human colon cancer cell line led to the isolation of seven sesquiterpene lactones, including the hitherto unknown isorolandrolide, 13-methoxyisorolandrolide (1), and bourbonenolide, 2alpha,13-diacetoxy-4alpha-hydroxy-8alpha-isobutyroyloxybourbonen-12,6alpha-olide (2), as well as five known compounds, 13-acetoxyrolandrolide (3), 8-desacyl-13-acetoxyrolandrolide-8-O-tiglate (4), 2-epi-glaucolide E (5), 2alpha,13-diacetoxy-4alpha-hydroxy-8alpha-methacryloyloxybourbonen-12,6alpha-olide (6), and 2alpha,13-diacetoxy-4alpha-hydroxy-8alpha-tigloyloxybourbonen-12,6alpha-olide (7). The structures of the two sesquiterpenes were elucidated on the basis of spectroscopic methods. All isolates were evaluated for their cytotoxicity using the HT-29 cell line, and only 13-acetoxyrolandrolide (3) was found to possess a potent inhibitory effect against this cell line. Compounds 3, 5 and 6 were also tested in a NF-kappaB (p65) inhibition assay, and 3 was assessed in an in vivo hollow fiber assay.

Succession After Disturbance of Lowland Mixed Dipterocarp Forest by Shifting Agriculture in East Kalimantan, Indonesia

A series of successional developments of lowland tropical forest in East Kalimantan after slash-and-burn for agriculture was assessed. These agricultural activities resulted in decreasing number of species, percentage of cover, frequency of seedling and sproutings. It is suggested that the initial seedlings play a major role in vegetation recovery of a tropical forest. The species composition changes along the successional gradients (i.e., reducing the proportion of pioneers vs increasing the primary forest species). Repeated burning for agriculture however, would change the forest community into Imperata grassland.