Synergistic Interactions Among Flavonoids And Acetogenins In Graviola (Annona Muricata) Leaves Confer Protection Against Prostate Cancer.
Carcinogenesis. 2015 Apr 11. Epub 2015 Apr 11. PMID: 25863125
Phytochemical complexity of plant extracts may offer health-promoting benefits including chemotherapeutic and chemopreventive effects. Isolation of"most-active fraction"or single constituents from whole extracts may not only compromise the therapeutic efficacy but also render toxicity, thus emphasizing the importance of preserving the natural composition of whole extracts. The leaves of Annona muricata, commonly known as Graviola, are known to be rich in flavonoids, isoquinoline alkaloids and annonaceous acetogenins. Here we demonstrate phytochemical synergy among the constituents of Graviola leaf extract (GLE) compared to its flavonoid-enriched (FEF) and acetogenin-enriched (AEF) fractions. Comparative quantitation of flavonoids revealed enrichment of rutin (~7-fold) and quercetin-3-glucoside (Q-3-G, ~3-fold) in FEF compared to GLE. In vivo pharmacokinetics and in vitro absorption kinetics of flavonoids revealed enhanced bioavailability of rutin in FEF compared to GLE. However, GLE was more effective in inhibiting in vitro prostate cancer proliferation, viability and clonogenic capacity compared to FEF. Oral administration of 100 mg/kg bw GLE showed ~1.2-fold higher tumor growth-inhibitory efficacy than FEF in human prostate tumor xenografts although the 44 concentration of rutin and quercetin-3-glucoside was more in FEF. Contrarily, AEF, despite its superior in vitro and in vivo efficacy, resulted in death of the mice due to toxicity. Our data indicate that despite lower absorption and bioavailability of rutin, maximum efficacy was achieved in the case of GLE, which also comprises of other phytochemical groups including acetogenins that make up its natural complex environment. Hence, our study emphasizes on evaluating the nature of interactions among Graviola leaf phytochemcials for developing favorable dose regimen for prostate cancer management to achieve optimal therapeutic benefits.