IN VITRO EVALUATION OF HYPOLIPIDEMIC EFFECT OF EXTRACTS OF MEDICINAL DRACAENA CINNABARI BALF. F. RESIN

Objective: The objective of the study was to in vitro evaluate of hypolipidemic effect of extracts of medicinal Dracaena cinnabari Balf. f. resin. Methods: About 800 g of dry powder of the resin of dracaena cinnabar was taken in a Soxhlet apparatus and subjected for sequential extraction of solvents from non-polar to polar end (hexane, benzene, diethyl ether, dichloromethane, chloroform, ethyl acetate, acetone, ethanol, methanol, and water); the extract samples were kept at 4°C for further assays. All the extracts were subjected to glucose uptake assay. Results: The ethanol extract showed significant (p<0.05) hypolipidemic effect by decreasing the activity of enzyme such as significant reduction in the pancreatic lipase enzyme, malic dehydrogenase enzyme, and glucose-6-phosphate dehydrogenase enzyme with IC50~13, ~13, and ~14, respectively. This results were similar to the standard drug atorvastatin with IC50~12, ~16, and ~17, respectively. Ethanol extract exhibited significant atherogenic index and percentage protection against hyperlipidemia. The potential biological activity of ethanol extract may be attributed to the highest polarity which needs further investigation.

Isolation, Characterization, and Expression Analysis of the MaMDH Gene in Banana

A full-length cDNA isolated from banana (Musa acuminata L. AAA group) fruit was named MaMDH, containing an open reading frame encoding 332 amino acids that represents the gene for cytoplasmic malic dehydrogenase (MDH). Sequence analysis showed that MaMDH shares high similarity with MDHs from castor bean (XP_002533463), tobacco (CAC12826), peach (AAL11502), and chickpeas (CAC10208). Real-time quantitative polymerase chain reaction (PCR) analysis of MaMDH spatial expression showed that it was expressed in all organs examined: roots, rhizomes, leaves, flowers, and fruits. The expression was the highest in flowers followed by the fruits and roots, whereas the rhizomes and leaves displayed the lowest expression levels. Real-time quantitative PCR revealed that MaMDH exhibited differential expression patterns in post-harvest banana fruits correlating with ethylene biosynthesis. In naturally ripened banana fruits, MaMDH expression was in accordance with ethylene biosynthesis. In accordance, for banana fruits treated with the ethylene analog 1-methylclopropene (1-MCP), MaMDH expression levels were inhibited and remained constant. After treatment with ethylene, MaMDH expression in banana fruits significantly increased with ethylene biosynthesis and peaked 3 days after harvest, which was 11 days earlier than that in naturally ripened banana fruits. These results suggest that MaMDH expression is induced by ethylene to regulate post-harvest banana fruits ripening.

Aspartate aminotransferase isotope exchange reactions: implications for glutamate/glutamine shuttle hypothesis

Aspartate aminotransferase (AAT) catalyzes amino group transfer from glutamate (Glu) or aspartate (Asp) to a keto acid acceptor—oxaloacetate (OA) or α-ketoglutarate (KG), respectively. Data presented here show that AAT catalyzes two partial reactions resulting in isotope exchange between3H-labeled Glu or 3H-labeled Asp and the cognate keto acid in the absence of the keto acid acceptor required for the net reaction. Tritiated keto acid product was detected by release of 3H2O from C-3 during base-induced enolization. Tritium released directly from C-2 (or C-3) by the enzyme was also evaluated and is a small fraction of that released because of exchange to the keto acid pool. Exchange is dependent on AAT concentration, time-dependent, proportional to the amino-to-keto acid ratio, and blocked by aminooxyacetate (AOA), an AAT inhibitor. Enzymatic conversion of [3H]KG to Glu by glutamic dehydrogenase (GDH) or of [3H]OA to malate by malic dehydrogenase (MDH) “protects” the label from release by base, showing that base-induced isotope release is from keto acid rather than a result of release during the exchange process. AAT isotope exchange is discussed in the context of the glutamate/glutamine shuttle hypothesis for astrocyte/neuron carbon cycling.