The antibacterial, antifungal and antioxidant effects of halloysite nanoclay, Cloisite 10A (C10A) and Cloisite 15A (C15A) organonanoclays were examined in this study. The antimicrobial action was assessed using the agar-well method and the disc diffusion method. The free radical-scavenging effects of the clays were determined using the 2,2-diphenyl-1-picrylhydrazyl method. Halloysite showed antimicrobial activity against Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus. C10A was effective against both Gram-positive bacteria (S. aureus, Listeria monocytogenes, Bacillus subtilis and E. faecalis) and Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae and P. aeruginosa). Additionally, only C10A was found to have an antimicrobial effect on Candida glabrata of 18 mm amongst the tested clays. C15A showed an antimicrobial effect on S. aureus and K. pneumoniae. It was determined that the antifungal properties of organoclays were higher than those of halloysite. The most effective clay type was determined to be C10A. The positively charged inner surface of the halloysite nanoclay can provide a large area to which negatively charged free radicals can attach. The modified C15A used in this study has two long-chain alkyl groups attached, whereas the modified C10A has a single long-chain alkyl group and a benzyl group attached. It is proposed that the differences in these antimicrobial effects are due to the structures of the molecules. According to these results, organoclays as green source materials could be used as additives and coatings in food processing, biomedical devices, filters and paints due to their antimicrobial and antioxidant properties.

Reuterin is a broad-spectrum antimicrobial substance produced by lactic acid bacteria, and most previous studies have reported that reuterin is only produced under anaerobic conditions. If there are lactic acid bacteria that also produce it under aerobic conditions, it could be applied to fermented foods. In this study, it was found that Lactobacillus coryniformis WBB05 showed optimal reuterin production (123 mM reuterin from 200 mM glycerol) when incubated aerobically at 20°C. Furthermore, the minimum inhibitory concentration (MIC) of reuterin was determined for starter lactic acid bacteria strains and cheese moulds. MIC toward Penicillium camemberti was 0.125 mM and the white mould starter was much more sensitive than other moulds.

Shattercane seed survival during soil burial was highly dependent on attached glumes. Shattercane seed tightly enclosed by glumes averaged 5 and 53% germination after 4 mo of winter burial in 1988 and 1989, respectively. Shattercane caryopses (seed without glumes) survival averaged 0.5 and 17% compared to 17 and 41% when treated with seed fungicides in 1988 and 1989, respectively. Shattercane caryopses tannin and lignin contents were higher than for cultivated sorghum caryopses. Glume tannin was four times higher and glume lignin was five times higher than in the caryopsis. Shattercane seed survival was positively correlated with glume tightness, caryopsis lignin, and glume tannin. Tannin and lignin appear to function as barriers to microbial invasion resulting in higher shattercane seed resistance to overwinter demise. Attempts to isolate fungal inhibitors from shattercane seed were unsuccessful.

Bioactive compounds of gonad, respiration tree, cuvierian organ, and body wall of the sea cucumber Holothuria leucospilota collected from the north coast of the Persian Gulf were extracted using ethyl acetate, methanol and water–methanol solvents. Extracts were evaluated for their antibacterial and antifungal activities against Aspergillus niger, Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. The activity was determined using the disc diffusion test. Cytotoxic activities of the extracts were determined by brine shrimp lethality assay. Results demonstrated that the A. niger was shown to be the most sensitive microorganism followed by C. albicans. The inhibition zone against A. niger and C. albicans had minimum inhibitory concentrations ranging from 3 to 7 μg/ml. The highest antifungal activity was found in G (water–methanol) with an inhibition zone of 50 mm against A. niger at 18 μg/ml extract concentration continuing with CT (methanol) with 46 mm inhibition zone against A. niger at 18 μg/ml extract concentration. The highest cytotoxic effect of methanol extract was found with LC50 values of about 40.31 μg/ml in the gonad organ from H. leucospilota continuing with the respiration tree organ with LC50 values of about 72.49 μg/ml.

The structure of hildecarpin, an insect antifeedant 6a-hydroxypterocarpan isolated from the roots of Tephrosia hildebrandtii has been confirmed by a combination of degradation reactions, NMR and mass spectra. Hildecarpin has been dehydrated to the corresponding pterocarpene 3-hydroxy-2-methoxy-8,9-methylenedioxypterocarpene. Hydrogenation and hydrogenolysis of the pterocarpene has afforded the isoflavan 2′, 7-dihydroxy-6-methoxy-4′,5′-methylenedioxyisoflavan, acetylation of which has led to 2′, 7-diacet6xy-6-methoxy-4′,5′-methylenedioxyisoflavan. The NMR and mass spectra of the degradation products confirm the structure previously assigned to hildecarpin.

A new 6a-hydroxylated pterocarpan, named hildecarpin, has been isolated from the healthy roots of Tephrosia hildebrandtii. It has been assigned the structure (−)-3, 6a-dihydroxy-2-methoxy-8, 9-methylenedioxypterocarpan on the basis of its spectroscopie data, optical rotation and chemical transformations. Hildecarpin has exhibited insect antifeedant activity against the legume pod-borer Maruca testulalis, an important pest of the cowpea (Vigna unguiculata), and antifungal activity against Cladosporium cucumerinum. This finding suggests that the pterocarpan phytoalexins formed as a result of microbial infection of the cowpea plant may constitute a basis for induced resistance in the plant against M. testulalis.

Three 9-acridone alkaloids, melicopicine, tecleanthine and 6-methoxy tecleanthine were isolated from the bark of Teclea trichocarpa. Melicopicine and tecleanthine exhibited mild antifeedant activity against the African armyworm, Spodoptera exempta. All the three alkaloids showed antimicrobial activity against the fungus, Cladosporium cucumerinum and the bacterium, Bacillus subtilis.