Biopesticide from tuber crop Elephant foot/yam against storage pest -

Biopesticide from tuber crop Elephant foot/yam against storage pest

                     Food grain losses due to insect infestation during storage and extension of shelf life period of the stored food grains during postharvest and storage period is a challenging task. The use of pesticides from biological origin is very important to control the food grain pest during storage and postharvest period. Raw material such as elephant foot yam (Amorphophallus paeoniifolious) is cheap and available throughout the year.  The extract from elephant foot yam will be a promising biopesticide against insects that infest stored food grains such as Sitophilus oryzae and Tribolium castaneum, thereby increasing the shelf life of the stored food grains and restoring the nutritional value of grains. The HPLC analysis of acetone extract confirmed the presence of flavonoids (area = 98.34%). Flavonoid constituent, 9,12-Octadecadienoic acid is found to have highest peak in the GC-MS analysis of acetone extract. The bioactive flavonoids, extracted from elephant foot yam against α-amylase were isolated, lyophilized, characterized, and quantified. Acetone extract of 0.25% concentration was found to be more efficient (100%) to repel S. oryzae and T. castaneum from wheat and moong dal within 48 hr and was confirmed by flour disc bioassay with FDI-90.47% within 24 hr for acetone extract. The objective of this study intended to extract α-amylase inhibitors from elephant foot yam, to characterize and evaluate their ability as potential insecticide against stored food grain pest.

Extraction of α-amylase inhibitors:

Elephant-foot yam of fresh and healthy corms was washed, sliced into cubes, and dried in a hot air oven for 24 hr powdered using a mortar and pestle. The dehydrated powder of elephant-foot yam was extracted with solvents (1:10, w/v), acetone on a shaker at 100 rpm for 48 hr at 37°C. The extracts were filtered and concentrated using a rotary evaporator. The concentrated extracts were lyophilized and stored at -20°C in a refrigerator.

Amylase and total flavonoids assay

The DNSA assay was performed to study amylase activity. Colorimetric technique of Aluminum chloride was used for flavonoids estimation.

Characterization of α-amylase inhibitors

The extracted compound was analyzed for the presence of flavonoids by GC-MS and HPLC. The necessary parameter and the condition required for carrying out the GC-MS analysis is set and the procedure is carried out.

Conclusion

These flavonoids were tested for amylase inhibition which gave positive result as α-amylase activity inhibitor. When α-amylase enzyme activity on starch metabolism was inhibited in the pest, carbohydrate ingested by the pest would not be converted to simple sugar which leads to starvation of the pest. α-amylase inhibition leads to reduction in the mobility and reproducibility of the insect. Hundred per cent repellency of S. oryzae in wheat and T. castaneum in moong dal were observed in the Cup bioassay, when treated with 0.25% of acetone extract of elephant foot yam within 48 hr. The flour disc bioassay also proved with Feeding deterrence index of about 90.47% within 24 hr for acetone extract of elephant foot yam. The elephant foot yam extract (acetone) could be a good alternative for the chemical insecticides, which is used to stored food grain pest control. Thus, the elephant foot yam extract helps to protect the stored food grains like wheat and mung dhal from the stored food grain pests. This product will increase the shelf life without changing the taste, odor, and color of the stored food grain and thereby preventing human health hazard.

Reference:

Vijayakumar, G. and BS, M., 2021. A potential biopesticide from Amorphophallus paeoniifolious to increase the shelf life of stored food grains. Journal of Food Processing and Preservation, 45(2), p: 15121.