Veranja Karunaratne

Antimicrobial alkaloids from Zanthoxylum tetraspermum and caudatum.

Two benzophenanthrene alkaloids, 8-acetonyldihydronitidine and 8-acetonyldihydroavicine were isolated from Zanthoxylum tetraspermum stem bark along with liriodenine, sesamin, lichexanthone and (+)-piperitol-gamma,gamma-dimethylallylether. The species endemic to Sri Lanka, Z. caudatum, contained sesamin, savinin, liriodenine, decarine and 8-O-desmethyl-N-nornitidine. 8-Acetonyldihydronitidine and 8-acetonyldihydroavicine showed significant antibacterial activity while the former along with liriodenine was strongly antifungal. Savinin exhibited potent spermicidal activity. Both savinin and sesamin exhibited significant insecticidal activity.

Ecdysterone from stem of Diploclisia glaucescens

Abstract The stem of Diploclisia glaucescens afforded ecdysterone in a high yield of over 3%. 13 C NMR of the tetraacetate and NOE studies on the triacetate provided further data on the structure and conformation of this phytoecdysteroid. Hemolytic, insecticidal and spermicidal activity are reported for the compound.

Antioxidant activity of some lichen metabolites.

Antioxidant activity of several classes of lichen metabolites were assessed in the in vitro superoxide radical (SOR), nitric oxide radical and 2,2-diphenyl-1-picrylhydrazil radical scavenging assays. The despsides sekikaic acid and lecanoric acid showed promising antioxidant activity in SOR assay with IC50 values of 82.0 ± 0.3 µmol and 91.5 ± 2.1 µmol, respectively, while the depsidone lobaric acid exhibited an IC50 value of 97.9 ± 1.6 µmol, all relative to the standard, propyl gallate (IC50 = 106.0 ± 1.7 µmol). One of the most abundant mononuclear phenolic compounds, methyl-β-orcinol carboxylate was found to be a potent NO scavenger (IC50 = 84.7 ± 0.1 µmol), compared to the standard rutin (IC50 = 86.8 ± 1.9 µmol).

Urea-Hydroxyapatite Nanohybrids for Slow Release of Nitrogen

While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by in situ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.

Chemistry and Bioactivity of Physciaceae Lichens Pyxine consocians and Heterodermia leucomelos

Abstract Cabraleadiol monoacetate, atranorin, methyl-β.-orcinolcarboxylate, zeorin, 4-O.-methylcryptochlorophaeic acid, and lichexanthone were isolated from the lichen Pyxine consocians Vainio... Heterodermia leucomelos (L)... Poelt contained a new triterpenoid, 6α-hydroxyhop-21β.H-22(29)-en, along with atranorin, zeorin, glyceryl trilinolate, and 3,6-dimethyl-2-hydroxy-4-methoxybenzoic acid. Cabraleadiol monoacetate, 4-O.-methylcryptochlorophaeic acid, lichexanthone, and 3,6-dimethyl-2-hydroxy-4-methoxybenzoic acid showed mosquito larvicidal activity against the second instar larvae of Aedes aegypti.. Lichexanthone exhibited human sperm motility enhancing activity.

1-[2′,4′-dihydroxy-3′,5′-di-(3″-methylbut-2″-enyl)-6′-methoxy] phenylethanone from Acronychia pedunculata root bark

Abstract A new arylketone, 1-[2′,4′-dihydroxy-3′,5′-di-(3″-methylbut-2″-enyl)-6′-methoxy] phenylethanone, was isolated together with acronylin, acrovestone, bergapten, β-amyrin and three furoquinoline alkaloids from the root bark of Acronychia pedunculata .

Methylenecyclopentane annulation: a synthesis of the sesquiterpenoid (±)-pentalenene

Transformation of the readily available keto acetal (10) into the novel sesquiterpenoid (±)-pentalenene (1) is accomplished via a 12-step synthetic sequence, the key conversion [(13) into (15)] of which involves a new, recently developed methylenecyclopentane annulation process.

General method for the synthesis of trishydroxamic acids

Abstract Triscarboxylic acids, when treated with hydroxylamines in the presence of water-soluble carbodiimide in THF-H 2 O, at pH≈4.8, yield the corresponding trishydroxamic acids in good yields.

Two fungicidal phenylethanones from Euodia lunu-ankenda root bark.

Abstract Euodia lunu-ankenda root bark contained two fungicidal phenylethanones, 1-[2′,4′-dihydroxy-6′-(3′-methyl-2′-butenyloxy)-5′-(3′-methyl-2′-butenyl)]phenylethanone and

An antifungal chromene from Eupatorium riparium

Abstract Methylripariochromene A (6-acetyl-7,8-dimethoxy-2,2-dimethylchromene), a root constituent of Eupatorium riparium , displayed antifungal activity against five of the seven fungal species tested. The chromene showed a toxicity to the fungus Colletotrichum gloeosporioides , a tropical pathogen, comparable to that of a commercial fungicide, although the chromene appeared to be fungistatic.