Pharmacokinetics of chlorogenic acid and rutin in larvae of Heliothis zea

Studies using [³H]chlorogenic acid and [³H]rutin demonstrated that the kinetics of uptake of these plant phenolics into the haemolymph of 5th-instar Heliothis zea (Boddie) following actue oral administration is a first-order process. The total quantity of either phenolic present in the haemolymph within 1 hr amounts to 5% or less of the total ingested dose. Based on TLC analyses, 80% or more of the radioactivity in the haemolymph occurs as the parent phenolic. Retention of [³H]-chlorogenic acid or [³H]-rutin in H. zea following chronic feeding from 1st to 3rd-instar larvae is also linearly related to dietary dose. Chlorogenic acid and rutin are both equitoxic and equivalent in bioavailability to H. zea.Loss of [³H]-rutin from the haemolymph of 5th-instar larvae following injection is biphasic. One half of the injected dose is excreted in the frass in the first 6 hr after injection; the other half is thereafter eliminated at 1/20th of the initial rate. Analyses of extracts of frass by thin-layer chromatography indicate that after either chronic or acute feeding 90% of the ingested phenolic is excreted unchanged. Possible sites and modes of action of phenolics in insects are discussed in light of these findings.