Prenylflavonols from the leaves of Macaranga sampsonii.

Four novel prenylflavonols, macaranones A-D (1-4), were isolated from the leaves of Macaranga sampsonii. Their structures were elucidated on the basis of spectroscopic data. Macaranones C (3) and D (4) represent first two examples of flavonols having an unusual peltogynoid skeleton which is formed from a 2'-geranylflavonol by cyclization between 3-OH and C-1'' of the 2'-geranyl substituent of the flavonol. Compounds 1-4 were evaluated for the cytotoxicity against several human cancer cell lines.

Photorhabdus luminescens toxin-induced permeability change in Manduca sexta and Tenebrio molitor midgut brush border membrane and in unilamellar phospholipid vesicle.

Photorhabdus luminescens, a Gram-negative bacterium, secretes a protein toxin (PL toxin) that is toxic to insects. In this study, the effects of the PL toxin on large receptor-free unilamellar phospholipid vesicles (LUVs) of Manduca sexta and on brush border membrane vesicles (BBMVs) of M. sexta and Tenebrio molitor were examined. Cry1Ac served as a positive control in our experiments due to its known channel-forming activity on M. sexta. Voltage clamping assays with dissected midguts of M. sexta and T. molitor clearly showed that both Cry1Ac and PL toxin caused channel formation in the midguts, although channel formation was not detected for T. molitor midguts under Cry1Ac and it was less sensitive to PL toxin than to Cry1Ac for M. sexta midguts. Calcein release experiments showed that both toxins made LUVs (unilamellar lipid vesicles) permeable, and at some concentrations of the toxins such permeabilizing effects were pH-dependent. The lowest concentrations of PL toxin were more than 600-fold and 24-fold lower to induce BBMV permeability of T. molitor and M. sexta than those to induce calcein release from LUVs of M. sexta. These further support that PL toxin is responsible for channel formation in the larvae midguts. The lower concentration to induce permeability in BBMV than in LUV is, probably, attributable to that BBMV has PL toxin receptors that facilitate the toxin to induce permeabilization. Furthermore, our results indicate that the effects of PL toxin on BBMV permeability of M. sexta were not significantly influenced by Gal Nac, but those of Cry1Ac were. This implies that PL toxin and Cry1Ac might use different molecular binding sites in BBMV to cause channel formation.

Preparation and characterization of a truncated caricain lacking 41 residues from the N-terminal.

We purified an 18.8 kD protease from caricain solution. This protease was derived from caricain. It does not have the first 41 residues of the N-terminal sequence of caricain, and its N-terminal residue is Thr. Also, one of the disulfide bonds of caricain (cys22-cys63) was opened during the formation of the protease. We named this 18.8 kD protease caricain II. Caricain II has a wide pH range, and it is more sensitive to temperature changes than caricain. The proteolytic activity of caricain II is twice as much as that of caricain using casein as a substrate. However, caricain II has a low hydrolytic activity with N-benzoyl-L-arginine ethyl ester (BAEE) that is one of the special substrates of caricain. Our results indicate that caricain II is remarkably different from caricain and it can provide an improvement over caricain on the proteolytic activity.

Sesquiterpenes from the mycelial cultures of Dichomitus squalens.

Three new sesquiterpenes including a rearranged hirsutane, dichomitol (1), an aromadendrane, 2beta,13-dihydroxyledol (2), and a 1,10-seco-2,3-seco-aromadendrane, dichomitone (3), were isolated from mycelial solid cultures of Dichomitus squalens. Their structures were elucidated by spectroscopic methods, and their nematicidal activities against Bursaphelenchus xylophilus were assessed.