Quassin antifeedant activity

A series of quassinoids was tested for antifeedant activity against the aphid Myzus persicae (Hemiptera, Aphididae) as shown in Table 7. Isobrucein-B (5), brucein-B (75), brucein-C (76), glaucarubinone (77), and quassin (78) decreased feeding at concentrations <0.05% and isobrucein-A (79) was effective at 0.01%. However, only quassin (78) showed no phytotoxic effects. Therefore, Polonsky et al. concluded that quassin (78) was the most promising compound for further development [28]. 

Using 3rd instar larvae of the diamondback moth Plutella xylostella), the antifeedant and insecticidal activities of sixteen quassinoids were compared with those of known insect antifeedant chlorodimeform (= galecron), as shown in Table 16. The insecticidal activity of quassin (78) was higher than that of chlorodimeform, although its antifeedant activity was nearly identical to that of the reference compound [39]. 

Q. is used in the food industry as a bitter principle, according to legal regulations brandies may contain up to 50 mg/L Q. as bitter component. Q. has a bitter taste even at a dilution of 1 60 000. In mammals Q. can effect a decrease in heart rate and, at higher concentrations, muscular convulsions and paralyses. The commercially available quassin is a mixture of quassin, neoquassin, isoquassin, and 18-hydroxy-quassin. Q. can be used as a substitute for emetine hydrochloride (see ipecac alkaloids). Some pentacyclic Q. have antiviral, antiparasitic, insecticidal, antifeedant, amoebicidic, and anti-inflammatory activities. 

Quassinoids have attracted much attention due to the wide spectrum of biological activities that they display, viz., antimalarial, antifeedant, anti-inflanunatory, antiulcer, antipyretic, antifertility, antileukemic, cytotoxic activities, and induction of murine stem cell differentiation which have been widely reported [54-59]. We have demonstrated that quassin is a potent immunomodulatory tool that efficiently controls the estabhshment of leishmanial parasite within the host macrophages [60]. Our contention was that quassin could be used as a potential inununomodulator to generate the required immunity not only for the treatment of leishmaniasis but also for the treatment of other chronic infectious diseases. Subsequently, we had shown that both quassin and neoquassin can be used along with artesunate (a derivative of artemisinin) as combinatorial therapy against malaria [61]. 

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