Goniothalamus velutinus Airy Shaw belongs to the family Annonaceae which is known to have anticancer, antitumor and many other bioactivities. Natives of Sabah and Sarawak use root decoction of G. velutinus for the treatment of headache and food poisoning while the bark was used as a mosquito repellent. Bark and leaf extracts of this plant, obtained from Brunei Darussalam, were tested for phytochemical and antioxidant activities. Phytochemical screening of plant extracts revealed the presence of alkaloids, steroids, terpenoids and cardiac glycosides. Quantitative determination of total phenolics, total flavonoids, and various in vitro antioxidant activities (DPPH, ABTS and FRAP) of methanolic extract was carried out using colorimetric methods. The total phenolic content, expressed as mg of gallic acid equivalent (GAE) per gram of extract, was found to be 68 mg GAE/g and 78 mg GAE/g for bark and leaves respectively. The radical scavenging activity measurement, expressed in terms of EC 50 (effective concentration of extract in µg/mL that reduces DPPH absorbance to 50% as compared to negative control), for leaf and bark extracts was found to be 155 µg/mL and 204 µg/mL respectively. While standards trolox and ascorbic acid shows EC 50 value of 5 µg/mL and 4 µg/mL respectively. Trolox equivalent antioxidant capacity (TEAC) was measured using the ABTS and FRAP method. Result for bark and leaf extracts was 79 mg and 106 mg Trolox equivalent (TE)/g respectively for ABTS method. For FRAP assay, results for bark and leaf extracts were 80 and 89 mg TE/g respectively.

Bioassay-guided isolation studies on the extracts of yellow flowers of Tagetes patula L. against the Heterodera zeae were carried out to identify phytochemicals lethal to this economically important cyst nematode. In vitro investigation of a polar extract and fractions showing activity led to the isolation of phenolic compounds (flavonoids and phenolic acids). In the nonpolar extract, a few fatty acids, their methyl esters, and thiophenes (including α-terthienyl) were detected. In studies of compounds obtained commercially, α-terthienyl and gallic and linoleic acids showed 100% mortality at concentrations of 0.125% after 24 h. Assessment of structure-activity relationships revealed that an increase in the number of hydroxyl groups in phenolic acids increased the activity; with fatty acids, activity depended on chain length and the number and position of double bonds. Crude extracts of the flowers of different colors also have promising activity.

A B S T R A C TPeat collected from Panaga, Brunei Darussalam, shows strong affinity towards the adsorption of Congo red (CR) dye from aqueous solution. The adsorption capacity of Bruneian peat under optimized conditions of shaking time, settling time, and medium pH is determined to be 10.1 mg g −1 at equilibrium. Adsorption of CR on Bruneian peat follows monolayer adsorption with small contribution to multilayer formation qualifying the validity of the Redlich-Peterson model, which is further supported by error function determination. In addition, changes in peat structure and surface were studied using scanning electron microscopic and X-ray fluorescence techniques. Kinetics studies were in agreement with the pseudo-second-order model and the adsorption reaction proceeds according to intra-particle diffusion.

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