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 100mg/kg bw GLE showed ~1.2-fold higher tumor growth-inhibitory efficacy than FEF in human prostate tumor xenografts although the concentration of rutin and Q-3-G 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.

It is appreciated far and wide that increased and regular consumption of fruits and vegetables is linked with noteworthy anticancer benefits. Extensively consumed as a spice in foods and beverages worldwide, ginger (Zingiber officinale Roscoe) is an excellent source of several bioactive phenolics, including non-volatile pungent compounds such as gingerols, paradols, shogaols and gingerones. Ginger has been known to display anti-inflammatory, antioxidant and antiproliferative activities, indicating its promising role as a chemopreventive agent. Here, we show that whole ginger extract (GE) exerts significant growth-inhibitory and death-inductory effects in a spectrum of prostate cancer cells. Comprehensive studies have confirmed that GE perturbed cell-cycle progression, impaired reproductive capacity, modulated cell-cycle and apoptosis regulatory molecules and induced a caspase-driven, mitochondrially mediated apoptosis in human prostate cancer cells. Remarkably, daily oral feeding of 100 mg/kg body weight of GE inhibited growth and progression of PC-3 xenografts by approximately 56 % in nude mice, as shown by measurements of tumour volume. Tumour tissue from GE-treated mice showed reduced proliferation index and widespread apoptosis compared with controls, as determined by immunoblotting and immunohistochemical methods. Most importantly, GE did not exert any detectable toxicity in normal, rapidly dividing tissues such as gut and bone marrow. To the best of our knowledge, this is the first report to demonstrate the in vitro and in vivo anticancer activity of whole GE for the management of prostate cancer.

Docetaxel is the only FDA-approved first-line treatment for castration-resistant prostate cancer (CRPC) patients. Docetaxel treatment inevitably leads to tumour recurrence after an initial therapeutic response with generation of multinucleated polyploid (MP) cells. Here we investigated role of MP cells in clinical relapse of CRPC. Prostate cancer (PC-3) cells were treated with docetaxel (5 nM) for 3 days followed by a washout and samples were collected at close intervals over 35 days post drug washout. The tumorigenic potential of the giant MP cells was studied by implanting MP cells subcutaneously as tumour xenografts in nude mice. Docetaxel-induced polyploid cells undergo mitotic slippage and eventually spawn mononucleated cells via asymmetric cell division or neosis. Both MP and cells derived from polyploid cells had increased survival signals, were positive for CD44 and were resistant to docetaxel chemotherapy. Although MP cells were tumorigenic in nude mice, these cells took a significantly longer time to form tumours compared with parent PC-3 cells. Generation of MP cells upon docetaxel therapy is an adaptive response of apoptosis-reluctant cells. These giant cells ultimately contribute to the generation of mononucleated aneuploid cells via neosis and may have a fundamental role precipitating clinical relapse and chemoresistance in CRPC.

Dietary phytochemicals offer nontoxic therapeutic management as well as chemopreventive intervention for slow-growing prostate cancers. However, the limited success of several single-agent clinical trials suggest a paradigm shift that the health benefits of fruits and vegetables are not ascribable to individual phytochemicals, rather may be ascribed to synergistic interactions among them. We recently reported growth-inhibiting and apoptosis-inducing properties of ginger extract (GE) in in vitro and in vivo prostate cancer models. Nevertheless, the nature of interactions among the constituent ginger biophenolics, viz. 6-gingerol, 8-gingerol, 10-gingerol, and 6-shogoal, remains elusive. Here we show antiproliferative efficacy of the most-active GE biophenolics as single-agents and in binary combinations, and investigate the nature of their interactions using the Chou-Talalay combination index (CI) method. Our data demonstrate that binary combinations of ginger phytochemicals synergistically inhibit proliferation of PC-3 cells with CI values ranging from 0.03 to 0.88. To appreciate synergy among phytochemicals present in GE, the natural abundance of ginger biophenolics was quantitated using LC-UV/MS. Interestingly, combining GE with its constituents (in particular, 6-gingerol) resulted in significant augmentation of GE's antiproliferative activity. These data generate compelling grounds for further preclinical evaluation of GE alone and in combination with individual ginger biophenols for prostate cancer management.