Insecticidal activity of plant flavonoids

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Context: Caesalpinia bahamensis Lam. is a medicinal plant used by the Cuban population to treat renal and hepatic diseases. However, this species lacks scientific studies that support its biological applications. Aims: To evaluate the chemical composition and the antioxidant capacity of fractions obtained from the stem of Caesalpinia bahamensis Lam. Methods: A continuous extraction of the stem was made by maceration using a battery of solvents of increasing polarity: chloroform, ethyl acetate and methanol. All fractions were analyzed by TLC and phytochemical screening. The compounds of the chloroform fraction were identified by GC/MS, while the ethyl acetate and methanol fractions were characterized by UV-Vis spectroscopy. The antioxidant capacity was evaluated by the DPPH and FRAP assays. Results: Ten compounds were identified by GC/MS of the chloroform fraction, associated with fatty acids, terpenoids and phytosterols. The major compounds of this fraction were octacosanol, monopal...

Context: Caesalpinia bahamensis Lam. is a medicinal plant used by the Cuban population to treat renal and hepatic diseases. However, this species lacks scientific studies that support its biological applications. Aims: To evaluate the chemical composition and the antioxidant capacity of fractions obtained from the stem of Caesalpinia bahamensis Lam. Methods: A continuous extraction of the stem was made by maceration using a battery of solvents of increasing polarity: chloroform, ethyl acetate and methanol. All fractions were analyzed by TLC and phytochemical screening. The compounds of the chloroform fraction were identified by GC/MS, while the ethyl acetate and methanol fractions were characterized by UV-Vis spectroscopy. The antioxidant capacity was evaluated by the DPPH and FRAP assays. Results: Ten compounds were identified by GC/MS of the chloroform fraction, associated with fatty acids, terpenoids and phytosterols. The major compounds of this fraction were octacosanol, monopalmitin and palmitic acid. The presence of flavonoids in the ethyl acetate and methanol fractions was demonstrated by phytochemical screening, TLC and UV spectroscopy. The three fractions showed antioxidant capacity in the DPPH assay, with the methanol fraction (IC50=11.1 µg/mL) being the most active. The ethyl acetate fraction (equivalent to 100.7 µmol ascorbic acid) and the methanol fraction (equivalent to 37.3 µmol ascorbic acid) showed antioxidant capacity in the FRAP assay at concentrations of 125 µg/mL and 1000 µg/mL, respectively. Conclusions: The fractions evaluated showed antioxidant capacity in the DPPH and FRAP assays, possibly associated with the presence of phenols and flavonoids.

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is one of the major insect pests of stored grains. Due to export legislation and zero-tolerance for live insect in trade commodities, extensive use of synthetic insecticides is in practice in order to eliminate pest infestations from the lots. Currently, the one and only acceptable chemical to be used in stored grain is phosphine but due to its excessive usage the stored grain pests are becoming resistant against it. Hence discovery of alternative compounds is much needed. In this study we have compared insecticidal efficacy of different plant materials from six commonly grown plants of Pakistan, viz. Allium sativum (Alliaceae), Zingiber officinale (Zingiberaceae), Cymbopogon citratus (Poaceae), Eucalyptus globulus (Myrtaceae), Nicotiana tabacum (Solanaceae), and Azadirachta indica (Meliaceae) against T. castaneum infesting stored wheat, rice, corn and gram pulse. Various plant parts were dried, powdered, and used as admixtures to the stored commodities in the experiments. The results have suggested that A. sativum (garlic) and Z. officinale (ginger) were more effective resulting into 15 times higher adult mortality and 4 to 5 times reduction in grain weight losses when mixed with rice grains. Similarly, A. indica when admixture with wheat checked the population growth in the resources resulting into 3.5 times less adult production compared to controls. A subsequent experiment was conducted to study the dose response of neem seed powder against the beetle pest infesting milled products. Surprisingly, better control was observed either at lowest (1% w/w) or the highest doses (5% w/w). This finding is of great interest to understand the underlying phenomenon which we assume is the ability of T. castaneum to feed selectively in flour mediums, however, further research on this aspect is required to be investigated. The results of this study support the use of botanicals for stored product pest management. Ó 2018 Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).