Analysis of glycoalkaloid distribution in the tissues of mealworm larvae (Tenebrio molitor)

Abstract Solanine (SOL) and chaconine (CHA) are glycoalkaloids (GAs) produced mainly by Solanum plants. These plant secondary metabolites affect insect metabolism; thus, they have the potential to be applied as natural plant protection products. However, it is not known which GA concentration induces physiological changes in animals. Therefore, the aim of this study was to perform a quantitative analysis of SOL and CHA in the larvae of Tenebrio molitor using LC‒MS to assess how quickly they are eliminated or metabolised. In this experiment, the beetles were injected with 2 μL of 10−5 M SOL or CHA solution, which corresponds to a dosage range of 0.12–0.14 ng/mg body mass. Then, 0.5, 1.5, 8, and 24 h after GA application, the haemolymph (H), gut (G), and the remainder of the larval body (FB) were isolated. GAs were detected in all samples tested for 24 h, with the highest percentage of the amount applied in the FB, while the highest concentration was measured in the H sample. The SOL and CHA concentrations decreased in the haemolymph over time, while they did not change in other tissues. CHA had the highest elimination rate immediately after injection, while SOL slightly later. None of the GA hydrolysis products were detected in the tested samples. One possible mechanism of the detoxification of GAs may be oxidation and/or sequestration. They may be excreted by Malpighian tubules, with faeces or with cuticles during moulting. The results presented are significant because they facilitate the interpretation of studies related to the effects of toxic substances on insect metabolism

Solanaceae glycoalkaloids: α-solanine and α-chaconine modify the cardioinhibitory activity of verapamil

Many plants from various genera produce secondary metabolites which have high biological activity as α-solanine and α-chaconine — glycoalkaloids from the Solanaceae family. In plants, they act as a natural weapon against herbivorous and as antipathogenic agents during fungal or bacterial infection. Thus, they are of interest to many researchers searching for new pharmacologically active compounds with the potential for use as drugs in therapies of different diseases. Moreover, they are commonly found in popular agricultural products like tomatoes, potatoes, or eggplants, and therefore, they may be consumed in quite high amounts. Because of their biological activity, glycoalkaloids may interact with many drugs used in therapies of various disorders. In our studies, we wanted to check, if Solanaceae glycoalkaloids, α-solanine, and α-chaconine, interact with popular drug verapamil, a calcium channel blocker used in the treatment of hypertension and as an antiarrhythmic drug, and in this way change its effectiveness. Our studies conducted on insect myocardium showed, that glycoalkaloids act antagonistically to this drug. They decreased the maximal effects evoked by pure verapamil and changed the pharmacokinetic parameters of verapamil action; hence, it seems that the consumption of glycoalkaloid-reach products during verapamil administration should be considering. Moreover, the analysis of L-type calcium channel transcript distribution in insect tissues indicated the presence of two splicing variants, one more present in the myocardium, and the second one in the nervous system