This study evaluated the feasibility of using methyl ester prepared from waste cooking oil for electrical insulation in distribution transformers. Methyl ester is produced by a transesterification reaction between waste cooking oil and methanol using sodium hydroxide as a catalyst. The physicochemical parameters and breakdown voltage of the methyl ester were determined. The effects of ageing on breakdown voltage, viscosity and acid value of methyl ester were also investigated. In addition, the breakdown voltage of Kraft paper impregnated with methyl ester was determined. Experimental results showed that methyl ester from waste cooking oil had low viscosity (5.17 cSt) and high breakdown voltage (40.3 kV). Other parameters also meet ASTM D6871 except for the pour and flash points. Ageing insignificantly affected the breakdown voltage of the methyl ester. After ageing, the breakdown voltage of the methyl ester increased to 42.1 kV. However, the viscosity of the methyl ester also increased by 23.5% and the acid value increased by 79.2 times. Finally, the breakdown voltage of Kraft paper impregnated with the methyl ester was about 5-10% lower than that of paper impregnated with the mineral oil.

From the methanol extract of Bischofia javanica Blume leaves, five compounds including 5'-β-D-glucopyranosyloxyjasmonic acid methyl ester (1) (3), friedelan-3-one (4), and gallic acid (5) were isolated. Their structures were elucidated by NMR spectra as well as in comparison with previously reported data. This is the first report on the isolation of 1, 2, and 3 from Bischofia javanica.

Morphological and microscopical characteristics of “Chua me dat hoa vang” collected in Ha Tinh province were studied. Results have identified the scientific name of the plant as Oxalis corniculata L. (family Oxalidaceae). Besides, the morphological characteristics and powder microscopy of leaf and stem of Oxalis corniculata L. species were established. Morphological characteristics of leaf and stem are pale yellow corolla, slightly pointed bracts and cube calcium oxalate crystals scattered in the soft tissue of the leaf. characteristics of herbal powder are twisted vascular grafts, hairs unicellular. Keywords Oxalis corniculata, Oxalis corniculata L., Oxalis, Oxalidaceae, morphological characteristics, microscopical characteristics. References [1] D.H. Bich, D.Q. Chung, B.X. Chuong, N.T. Dong, D.T. Dam, P.V. Hien, V.N. Lo, P.D. Mai, P.K. Man, D.T. Nhu, N. Tap, T. Toan, Medicinal plants and animals in Vietnam, Volume I, Science and Technology Publishing House, Hanoi, 2004. (in Vietnamese)[2] M. Ibrahim, I. Hussain, M. Imran, N. Hussain, A. Hussain, T. Mahboob, Corniculatin A, a new flavonoidal glucoside from Oxalis corniculata, Revista Brasileira de Farmacognosia 23(4) (2013) 630-634. https://doi.org/10.1590/S0102- https://doi.org/10.1590/S0102695X2013005000059.[3] K.C. Oberlander, E. Emshwiller, D.U. Bellstedt, L.L. Dreyer, A model of bulb evolution in the eudicot genus Oxalis (Oxalidaceae), Molecular Phylogenetics and Evolution 51(1) (2009) 54–63. https://doi.org/10.1016/j.ympev.2008.11.022.[4] J. Zietsman, L.L. Dreyer, B. Jansen, V. Vuuren, Genetic differentiation in Oxalis (Oxalidaceae): A tale of rarity and abundance in the Cape Floristic Region, South African Journal of Botany, 75(1) (2009) 27–33. https://doi.org/10.1016/j.sajb.2008.06.003[5] L.D. Bich, Good folk remedies, Ethnic Culture Publishing House, Hanoi, 2000 (in Vietnamese).[6] L.D. Bich, T.V. On, Botany, Medical Publishing House, Hanoi, 2007 (in Vietnamese).[7] D.T. Loi, Vietnamese medicinal plants and herbs, Medical Publishing House, Hanoi, 2005 (in Vietnamese).[8] N.V. Than, Laboratory of Medicinal Materials by microscopic method, Science and Technology Publishing House, Hanoi, 2003 (in Vietnamese).