In Vitro Screening of East Asian Plant Extracts for Potential Use in Reducing Ruminal Methane Production

Indiscriminate use of antibiotics can result in antibiotic residues in animal products; thus, plant compounds may be better alternative sources for mitigating methane (CH₄) production. An in vitro screening experiment was conducted to evaluate the potential application of 152 dry methanolic or ethanolic extracts from 137 plant species distributed in East Asian countries as anti-methanogenic additives in ruminant feed. The experimental material consisted of 200 mg total mixed ration, 20 mg plant extract, and 30 mL diluted ruminal fluid-buffer mixture in 60 mL serum bottles that were sealed with rubber stoppers and incubated at 39 °C for 24 h. Among the tested extracts, eight extracts decreased CH₄ production by >20%, compared to the corresponding controls: stems of Vitex negundo var. incisa, stems of Amelanchier asiatica, fruit of Reynoutria sachalinensis, seeds of Tribulus terrestris, seeds of Pharbitis nil, leaves of Alnus japonica, stem and bark of Carpinus tschonoskii, and stems of Acer truncatum. A confirmation assay of the eight plant extracts at a dosage of 10 mg with four replications repeated on 3 different days revealed that the extracts decreased CH₄ concentration in the total gas (7-15%) and total CH₄ production (17-37%), compared to the control. This is the first report to identify the anti-methanogenic activities of eight potential plant extracts. All extracts decreased ammonia (NH₃-N) concentrations. Negative effects on total gas and volatile fatty acid (VFA) production were also noted for all extracts that were rich in hydrolysable tannins and total saponins or fatty acids. The underlying modes of action differed among plants: extracts from P. nil, V. negundo var. incisa, A. asiatica, and R. sachalinensis resulted in a decrease in total methanogen or the protozoan population (p < 0.05) but extracts from other plants did not. Furthermore, extracts from P. nil decreased the population of total protozoa and increased the proportion of propionate among VFAs (p < 0.05). Identifying bioactive compounds in seeds of P. nil by gas chromatography-mass spectrometry analysis revealed enrichment of linoleic acid (18:2). Overall, seeds of P. nil could be a possible alternative to ionophores or oil seeds to mitigate ruminal CH₄ production.

Evaluation of the acaricidal toxicities of camphor and its structural analogues against house dust mites by the impregnated fabric disc method

BACKGROUND

The acaricidal activities of (±)-camphor structural analogues against house dust mites were evaluated using the impregnated fabric disc bioassay.

RESULTS

The acaricidal effects of camphor and its structural analogues were evaluated against Dermatophagoides farinae and D. pteronyssinus. Based on the LD50 values against D. farinae, (±)-camphor (0.95 µg cm(-2) ) was 38.75 times more effective than N,N-diethyl-m-toluamide (DEET) (36.81 µg cm(-2) ), followed by (+)-camphor (1.41 µg cm(-2) ), (-)-camphor (2.03 µg cm(-2) ) and (1R)-camphor oxime (3.31 µg cm(-2) ) in the impregnated fabric disc bioassay. However, camphor-10-sulfonic acid and camphoric acid had no observable activity against D. farinae or D. pteronyssinus. The acaricidal activities of camphor and its structural analogues against D. pteronyssinus were similar to those against D. farinae.

CONCLUSION

These results indicate that camphor and its structural analogues are suitable for producing acaricidal agents against house dust mites.

Acaricidal activities of bicyclic monoterpene ketones from Artemisia iwayomogi against Dermatophagoides spp

The acaricidal properties of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one isolated from Artemisia iwayomogi and its structural analogues were evaluated against Dermatophagoides farinae and D. pteronyssinus, and their effects were compared with that of the commercial acaricide benzyl benzoate. Based on the 50 % lethal dose (LD50) values against D. farinae, 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (0.82 μg/cm(2)) was 9.71 times more effective than benzyl benzoate (7.96 μg/cm(2)), followed by (1R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (1.03 μg/cm(2)), (1S)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (1.58 μg/cm(2)), and (1R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one oxime (3.05 μg/cm(2)) in a filter paper bioassay. The acaricidal activities of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one and its structural analogues against D. pteronyssinus were similar to those against D. farinae. These results demonstrate that naturally occurring A. iwayomogi-isolated 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one and its structural analogues are suitable for the production of natural acaricides against house dust mites.