| olyethylene glycol (PEG) possesses a number of interesting properties, including its solubility in both water and certain organic solvents. Since PEG is non-toxic and weakly immunogenic, it is currently used for biomedical and biotechnical applications. Twenty PEG conjugate adducts modified from several natural products such as artemisinin, betulin, limonin, amyrin and quinoline derivatives have been prepared by the attachment of PEG through ester, ether and amide linkage. Among them, five PEG-artemisinin conjugates showed about 5-100 times more potent antimalarial activities than artemisinin itself by in vitro and vivo screening against two Plasmodium falciporum clones, Indochina III (W-2) and Sierra Leone I (D-6).;The PEG-artemisinin esters exhibited higher activities than the ether derivative. In addition, as molar peroxide content of PEG-artemisinin adducts decrease, biological activities were decreased. Four PEG-betulin conjugate esters were obtained by the coupling of PEG-carboxylic acid with several key intermediates synthesized by the modification of the 19-side-chain and A- and E-ring from betulin. Three PEG-limonoid conjugate adducts. which were structurally modified A-, B- and D-ring analogus of limonin, have been prepared and evaluated as antifeedant against 4th instar Colorado potato-beetle, Leptinotarsa decenlineata (Say). The antifeedant activities of PEG-limonin ester adducts were reduced about 40-60% compared to the corresponding limonoids respectively.;Two triterpenes,... |
