Sequestration of Camptothecin, an Anticancer Alkaloid, by Chrysomelid Beetles

Laboratory and field evaluations of camptothecin sodium salt against phytophagous mites

BACKGROUND

Camptothecin (CPT), a monoterpene indole alkaloid from Camptotheca acuminate (Nyssaceae), is toxic to some insect pests but insoluble in water. Here we show that an aqueous CPT-Na(+) solution can kill the phytophagous mites Tetranychus urticae (TU), Acaphylla theae (AT) and Brevipalpus obovatus (BO) under laboratory and field conditions.

RESULTS

Modelling of 10 day time-concentration-mortality responses of female adults to 2 mL tower sprays of three CPT-Na(+) dilutions generated LC50 and LT50 values that decreased over post-spray days and sprayed amounts respectively. CPT-Na(+) sprays required to kill 50% BO, TU and AT were 35, 41 and 124 µg mL(-1) on day 1 post-spray, but rapidly decreased to 2.2, 2.5 and 3.6 µg mL(-1) on day 5, and to 0.69, 0.77 and 1.17 µg mL(-1) on day 7 respectively. In summer field trials, a spray rate of 7.5 g CPT-Na(+) ha(-1) provided better control efficacy against TU (81-85%) on cotton or AT (90-93%) and BO (83-88%) in tea gardens than aramite (commercial acaricide) at the labelled rate of 56.25 g ha(-1) . Half of the CPT-Na(+) rate controlled the mites as effectively as aramite.

CONCLUSION

Water-soluble CPT-Na(+) is a promising plant-sourced acaricide to combat wide-spectrum pest mites.

Evodiamine and rutaecarpine alkaloids as highly selective transient receptor potential vanilloid 1 agonists

Despite that among non-camptothecin natural products promising anticancer therapeutics are evodiamine derivatives, involved into mechanism of physiological function of topoisomerase-I. But, more recent findings have been shown that substituted quinazole alkaloids act as transient receptor potential vanilloid 1 agonists. The TRP(V1) is a calcium ion channel, activated by pH, heat and inflammatory activators. I is implicated in pain sensing. TRPV1 agonist is capsaicine (1). Both 1 and evodiamine (2), therefore, produce same physiological response, but are structurally unrelated from chemical viewpoint. Furthermore precise mechanistic aspects of drugs receptor interactions are still not fully understood. This study is the first one, which provides assessment of molecular factors contributing significantly to selectivity of 2 and rutaecarpine (3) as well as their twenty-two new functionalized derivatives towards (TRP)V1. The suggested new functionalization type of molecular skeleton, which is completely different one in respect the known derivatives, which is implicated in treatment of variety of cancer cell lines interacting preferably with topoisomerase-I. It resulted to increasing of the binding affinity and selectivity of the functionalized derivatives specifically to (TRP)V1∈1.36-1.72 and ∈2.50-3.16 higher than 1-3.

Untapped mutualistic paradigms linking host plant and endophytic fungal production of similar bioactive secondary metabolites

The biosynthetic potential of endophytic fungi has gained impetus in recent times owing to the continual discovery of fungal endophytes capable of synthesizing plant compounds. However, the sustained production of the desired plant compounds has not yet been achieved using endophytes. It is thus imperative to investigate the diverse interactions that endophytes have with coexisting endophytes, host plants, insect pests, and other specific herbivores. The precise role of these associations on the endophytic production of host plant compounds is mostly overlooked and open to future discoveries. Here, highlighted are the implications of the poorly investigated links and molecular mechanisms that might trigger similar chemical responses in both plants and endophytes. Elucidating such connections can not only enhance the understanding of evolution of complex defense mechanisms in plants and associated organisms, but also help in the sustained production of plant compounds using endophytes harbored within them.