Obtention of biodiesel through an enzymatic two-step process. Study of its performance and characteristic emissions.

We describe the enzymatic synthesis of biodiesel from waste cooking oil (WCO) in a two-step production process: hydrolysis of WCO, followed by acid-catalyzed esterification of free fatty acids (FFAs). Among the three commercial enzymes evaluated, the inexpensive lipase Lipex® 100L supported on Lewatit® VP OC 1600 produced the best overall biodiesel yield (96.3%). Finally, we assessed the combustion efficiency of the obtained biodiesel and its blends. All blends tested presented lower emissions of CO and HC compared to diesel. The NOx emissions were higher due to biodiesel's high volatility and viscosity. The cost of biodiesel production was calculated using the process described.

Quinone derivatives by chemical transformations of 16-hydroxycarnosol from Salvia species.

The known diterpenes 12,16-epoxycarnosol (2), isotanshinone II (6), and (+)-neocryptotanshinone (8) were obtained by partial synthesis from 16-hydroxycarnosol (1), a C-16 hydroxylated abietatriene diterpene isolated in relative abundance from the aerial part of Salvia mellifera GREENE. The physical and spectroscopic data of these semisynthetic diterpenes were identical to those given for the natural ones in the literature. These abietane diterpenes have very interesting biological activities and the semisynthetic approach described here represents an alternative to obtain them from other major diterpenes isolated from Salvia species. Additionally, seven new semisynthetic diterpene analogues, 11,14-dioxo-12,16-epoxy-8,12-abietadien-20,7beta-olide (3), 11,14-dioxo-12,16-epoxy-8,12,15(16)-abietatrien-20,7beta-olide (4), 15,16-didehydro-12,16-epoxycarnosol (5), 1-oxoisotanshinone II (7), 16-hydroxycolumbaridione (9), 12,16-diacetoxycolumbaridione (10), and 14-methoxy-12,16-epoxycarnosol (13), were obtained from 1. The structures of the new compounds were established based on their spectroscopic data.