Polyphenolic compounds of Mediterranean Lamiaceae and investigation of orientational effects on Acanthoscelides obtectus (Say)

Abstract

As a continuation of work on Mediterranean aromatic plants with insecticidal properties, the hydrodistillate fraction of five species of Lamiaceae showing insecticidal effects on Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae) was analysed to determine if polyphenols were involved in the toxic effect. Chromatographic analyses indicated that the polyphenols were mainly cinnamic acids and flavones, the most abundant being rosmarinic acid, luteolin-7-glucoside and derivatives. A bioassay to assess the effect on the behaviour and survival of beetles was conducted with these main compounds compared to other polyphenolic acids and flavonoids (flavones, flavanones, flavonols and flavanols) aglycones and glycosides. The polyphenols tested were toxic to the beetles to different degrees. Caffeic and ferulic acids, vanillin and luteolin-7-glucoside induced a knockdown effect on the first day, gallic acid on the second day. Quercetin significantly decreased natural mobility from the first day, naringin, syringaldehyde, vanillic acid and gallic acid after the 4th day. On the 8th day all compounds caused significant mortality. Rosmarinic acid and luteolin-7-glucoside were the most active compounds. An attractive effect enhanced the toxicity.