Antibacterial and synergistic activity of 6ß-hydroxy-3-oxolup-20(29)-en-28-oic acid (6ß-hydroxy betunolic acid) isolated from Schumacheria castaneifolia vahl.

Multi- drug resistant microbial pathogens are a serious global health problem and thus new antibacterial agents, which are effective both alone and in combination with traditional antibiotics, are urgently needed. Hence, the objective of the present study was to investigate the antibacterial activity of 6ß-hydroxy-3-oxolup-20(29)-en-28-oic acid (6ß-hydroxy betunolic acid) isolated from the bark of Schumacheria castaneifolia and its effect when combined with oxacillin. Antibacterial potential of 6ß-hydroxy betunolic acid alone was performed using broth micro dilution assay against sixteen bacterial strains which included eight standard strains [Staphylococcus aureus (ATCC 29213 and ATCC 25923), Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 35218 and ATCC 25922), carbapenemase producing Kebsiella pneumonia (ATCC BAA 1705), carbapenemase non-producing K. pneumonia (ATCC BAA 1706) and Pseudomonas aeruginosa (ATCC 27853)] and four strains each of clinically isolated meropenem resistant Acinetobactor sp. and methicillin resistant S. aureus (MRSA) which were included in the urgent threat list and serious threat list, respectively in 2019 by the Centers for Disease Control and Prevention in the United States. Its effect when combined with oxacillin was tested against S. aureus (ATCC 29213) and MRSAs using a checkerboard dilution method. The results indicated that 6ß-hydroxy betunolic acid had antibacterial activity against the tested Gram positive organisms with MICs ranging from 16 to 32 mg L-1 (MIC of oxacillin and meropenem ranged from 0.25-16 and 0.03-128 mg L-1 respectively). The high MIC values (>1024 mg L-1) of 6ß-hydroxy betunolic acid against Gram negative strains indicated a likely lack of activity. Further, 6ß-hydroxy betunolic acid exhibited synergistic effect with oxacillin against Staphylococcus aureus (0.49) and showed an additive effect against all the tested MRSAs. The present study suggested that the antibacterial activity of the 6ß-hydroxy betunolic acid is restricted to Staphylococcus isolates and possibly Enterococcus faecalis. Further testing on different types of Gram positives and identification of the exact mechanism of action would be of importance.

Alginate nanoparticles protect ferrous from oxidation: Potential iron delivery system.

A novel, efficient delivery system for iron (Fe2+) was developed using the alginate biopolymer. Iron loaded alginate nanoparticles were synthesized by a controlled ionic gelation method and was characterized with respect to particle size, zeta potential, morphology and encapsulation efficiency. Successful loading was confirmed with Fourier Transform Infrared spectroscopy and Thermogravimetric Analysis. Electron energy loss spectroscopy study corroborated the loading of ferrous into the alginate nanoparticles. Iron encapsulation (70%) was optimized at 0.06% Fe (w/v) leading to the formation of iron loaded alginate nanoparticles with a size range of 15-30nm and with a negative zeta potential (-38mV). The in vitro release studies showed a prolonged release profile for 96h. Release of iron was around 65-70% at pH of 6 and 7.4 whereas it was less than 20% at pH 2.The initial burst release upto 8h followed zero order kinetics at all three pH values. All the release profiles beyond 8h best fitted the Korsmeyer-Peppas model of diffusion. Non Fickian diffusion was observed at pH 6 and 7.4 while at pH 2 Fickian diffusion was observed.

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.

Two new lactones with mosquito larvicidal activity from three Hortonia species.

The structures of the butenolides 1 and 2, isolated from the endemic plants Hortonia floribunda, H. angustifolia, and H. ovalifolia, collected in Sri Lanka, have been elucidated by spectroscopic analysis. These compounds exhibited potent mosquito larvicidal activity against the second instar larvae of Aedes aegypti.

Triterpenoidal Constituents of Diploclisia glaucescens.

The pentacyclic triterpenoids serjanic acid and phytolaccagenic acid as well as a new glycoside, 3- O-beta- D-glucopyranosylphytolaccagenic acid have been isolated from the stem of DIPLOCLISIA GLAUCESCENS (Bl.) Diels (Menispermaceae). New spectroscopic data are furnished for serjanic acid and phytolaccagenic acid.