Evaluation of Natural and Synthetic Compounds from East Asiatic Folk Medicinal Plants on the Mediation of Cancer

Phytochemicals in Cancer Treatment and Cancer Prevention-Review on Epidemiological Data and Clinical Trials

Phytochemicals are a non-nutritive substances that are present in plants and contribute significantly to their flavor and color. These biologically active compounds are classified into five major groups, namely phenolics, carotenoids, organosulfur compounds, nitrogen-containing compounds, and alkaloids, and are known for their potential health benefits in the prevention of various diseases, including cancer. The purpose of this review article is to explore the potential therapeutic benefits of the dietary phytochemicals, such as flavonoids, phenolic acids, phytosterols, carotenoids, and stilbenes, in cancer treatment and prevention based on the epidemiological studies and clinical trials. Although the majority of epidemiological studies report a significant advantage of the heightened phytochemical consumption and increased serum levels of these compounds, linking increased exposure with a lower cancer risk across most cancer types, these effects could not be replicated in the most available clinical trials. In fact, many of these trials were withdrawn early due to a lack of evidence and/or risk of harm. Despite the strong anticancer effect of phytochemicals, as well as their proven efficacy in multiple epidemiological studies, there is still a great need for human studies and clinical trials, with great caution regarding the safety measures. This review article provides an overview of the epidemiological and clinical evidence supporting the potential chemopreventive and anticancer properties of phytochemicals, with a focus on the need for further research in this area.

Hibiscus cannabinus L. (kenaf) studies: Nutritional composition, phytochemistry, pharmacology, and potential applications

The electronic database was searched up to July 2020, using keywords, kenaf and roselle, chemical constituents of kenaf and roselle, therapeutic uses of kenaf and roselle. Journals, books and conference proceedings were also searched. Investigations of pharmacological activities of kenaf revealed that this edible plant exhibits a broad range of therapeutic potential including antioxidant, antimicrobial, antityrosinase, anticancer, antihyperlipidemia, antiulcer, anti-inflammatory, and hepatoprotective activities. Kenaf also showed versatile utility as a functional ingredient in food, folk medicine, and animal nutritions, as well as in nanotechnology processes. The exploitation of underexploited kenaf by-products can be a significant part of waste management from an economic and environmental point of view. In addition, kenaf showed comparable nutritional, phytochemical, and pharmacological properties with Hibiscus sabdariffa (Roselle). This review has important implications for further investigations and applications of kenaf in food and pharmaceuticals industry.

Angiotensin-1-converting enzyme inhibition, antioxidant activity, and modulation of cerebral Na+/K+ ATPase by free phenolics of African locust bean (Parkia biglobosa)

AIMS

To investigate the antioxidant activities and effects of free phenols (FPPB) and bound phenols (BPPB) of Parkia biglobosa leaves on some enzymes of neuro-cardiovascular relevance.

METHODS AND RESULTS

HPLC-DAD fingerprinting of FPPB and BPPB, and the antihemolytic, radical (1,1-diphenyl-2 picrylhydrazyl, DPPH; 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid), ABTS) scavenging and ferric reducing antioxidant properties of extracts, were assessed. In addition, the effects of the phenolics on angiotensin-1-converting enzyme (ACE), cerebral acetylcholinesterase/butyrylcholinesterase (AChE/BuChE), and Na+/K+ATPase were determined in vitro. FPPB was more potent than BPPB in terms of ABTS (EC50:4.06 ± 0.3 vs 24.07 ± 2.1 μg/mL) and DPPH (EC50:3.82 ± 0.2 vs 10.22 ± 0.1 μg/mL) radicals scavenged, respectively. The free phenolic extract was a better DPPH. scavenger than ascorbic acid (EC50 = 12.58 ± 0.4 μg/mL; DPPH reference) and compared well with Trolox (EC50:4.44 ± 0.08 μg/mL; ABTS reference). The anti-hemolytic effect of FPPB (36%) and BPPB (53%) was highest at 15 μg/mL but lower than that recorded for ascorbic acid (67% at 10 μg/mL). Even though FPPB (IC50 = 15.35 ± 4.0 μg/mL) and BPPB (IC50 = 46.85 ± 3.3 μg/mL) showed considerably lower ACE-inhibitory effect than ramipril (IC50:0.173 ± 0.04 μg/mL), both extracts demonstrated dose-dependent, significant (p < 0.01/p < 0.05) inhibition of the enzyme. FPPB increased cerebral Na+/K+ATPase activity but neither phenolic extract affects cerebral AChE/BuChE activities. HPLC-DAD revealed catechin, caffeic acid, and quercetin, respectively, as the major phenolics (mg/g) in FPPB (29.85, 30.29, and 17.10) and BPPB (32.70, 30.51, and 19.25).

CONCLUSION

The effects of P biglobosa on ACE and cerebral ATPase are related to its constituent phenolics. ACE inhibition could be an important mechanism underlying the documented hypotensive effect of the plant.

Mechanism of Action of Two Flavone Isomers Targeting Cancer Cells with Varying Cell Differentiation Status

Apoptosis can be triggered in two different ways, through the intrinsic or the extrinsic pathway. The intrinsic pathway is mediated by the mitochondria via the release of cytochrome C while the extrinsic pathway is prompted by death receptor signals and bypasses the mitochondria. These two pathways are closely related to cell proliferation and survival signaling cascades, which thereby constitute possible targets for cancer therapy. In previous studies we introduced two plant derived isomeric flavonoids, flavone A and flavone B which induce apoptosis in highly tumorigenic cancer cells of the breast, colon, pancreas, and the prostate. Flavone A displayed potent cytotoxic activity against more differentiated carcinomas of the colon (CaCo-2) and the pancreas (Panc28), whereas flavone B cytotoxic action is observed on poorly differentiated carcinomas of the colon (HCT 116) and pancreas (MIA PaCa). Apoptosis is induced by flavone A in better differentiated colon cancer CaCo-2 and pancreatic cancer Panc 28 cells via the intrinsic pathway by the inhibition of the activated forms of extracellular signal-regulated kinase (ERK) and pS6, and subsequent loss of phosphorylation of Bcl-2 associated death promoter (BAD) protein, while apoptosis is triggered by flavone B in poorly differentiated colon cancer HCT 116 and MIA PaCa pancreatic cancer cells through the extrinsic pathway with the concomitant upregulation of the phosphorylated forms of ERK and c-JUN at serine 73. These changes in protein levels ultimately lead to activation of apoptosis, without the involvement of AKT.

Synthesis and Antiviral Activity of Quercetin Brominated Derivatives

Reaction of quercetin (QR) (1) with bromine under various conditions was studied. Interaction of QR with 2–3 equiv. of bromine in glacial acetic acid at 35–40°C for 2–4 h and 20–22°C for 24 h led to the formation of QR 6,8-dibromide (2) (52–54% yields, 96–98% purity by HPLC). Interaction of QR with 2–5 equiv. bromine in absolute ethanol at 0–5°C and 20–22°C for 24 h led to the formation of 3- O-ethyl-QR-2,3,6,8,5′-pentabromide (3) (95–97% purity by HPLC) the output of which depends on the quantity of bromine. It was shown in MDCK cell culture that compound 2 exhibits a moderate inhibitory activity against pandemic influenza virus A/H1N1/pdm09 (EC50 6.0 μg/mL, CTD50 97.7 μg/mL, SI 16). Compound 3 was inactive.

Polyphenolics from peach (Prunus persica var. Rich Lady) inhibit tumor growth and metastasis of MDA-MB-435 breast cancer cells in vivo

The tumor growth inhibition and anti-metastatic effects of peach polyphenolics were investigated in vivo using a xenograft model and MDA-MB-435 breast cancer cells. Results showed that tumor growth and lung metastasis were inhibited in vivo by peach polyphenolics in a dose range of 0.8-1.6 mg/day, and these effects were mediated by inhibition of metalloproteinases gene expression. Modulation of metalloproteinase-2, metalloproteinase-3 and metalloproteinase-13 gene expression may be some of the molecular targets for anti-metastatic activity of peach polyphenolics. Therefore, these compounds may constitute a novel chemopreventive tool to reduce the risk of metastasis in the combination therapy when primary cancer is diagnosed. Conversion to equivalent human intake for future clinical studies using the body surface area normalization method gave a dose of ~370.6 mg/day for a human adult of 60 kg, which can be supplied by consuming two to three peach fruit per day or alternatively using a dietary supplement peach polyphenol extract powder.

Anti-neoplastic activity of two flavone isomers derived from Gnaphalium elegans and Achyrocline bogotensis

Over 4000 flavonoids have been identified so far and among these, many are known to have antitumor activities. The basis of the relationships between chemical structures, type and position of substituent groups and the effects these compounds exert specifically on cancer cells are not completely elucidated. Here we report the differential cytotoxic effects of two flavone isomers on human cancer cells from breast (MCF7, SK-BR-3), colon (Caco-2, HCT116), pancreas (MIA PaCa, Panc 28), and prostate (PC3, LNCaP) that vary in differentiation status and tumorigenic potential. These flavones are derived from plants of the family Asteraceae, genera Gnaphalium and Achyrocline reputed to have anti-cancer properties. Our studies indicate that 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays potent activity against more differentiated carcinomas of the colon (Caco-2), and pancreas (Panc28), whereas 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) cytototoxic action is observed on poorly differentiated carcinomas of the colon (HCT116), pancreas (Mia PaCa), and breast (SK-BR3). Both flavones induced cell death (>50%) as proven by MTT cell viability assay in these cancer cell lines, all of which are regarded as highly tumorigenic. At the concentrations studied (5-80 µM), neither flavone demonstrated activity against the less tumorigenic cell lines, breast cancer MCF-7 cells, androgen-responsive LNCaP human prostate cancer line, and androgen-unresponsive PC3 prostate cancer cells. 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays activity against more differentiated carcinomas of the colon and pancreas, but minimal cytotoxicity on poorly differentiated carcinomas of these organs. On the contrary, 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) is highly cytotoxic to poorly differentiated carcinomas of the colon, pancreas, and breast with minimal activity against more differentiated carcinomas of the same organs. These differential effects suggest activation of distinct apoptotic pathways. In conclusion, the specific chemical properties of these two flavone isomers dictate mechanistic properties which may be relevant when evaluating biological responses to flavones.

Synthesis and antitumor activity of lapathoside D and its analogs

Phenylpropanoid sucrose esters are important class of plant-derived natural products and have greater potential to be leads for new drugs because of their structural diversity and broad-array of pharmacological and biological activities. Regio- and chemo-selective acylation of 2,1':4,6-O-di-isopropylidene sucrose 4 with cinnamoyl chloride 5 and p-acetoxycinnamoyl chloride 6 afforded mono-, di-, tri- and tetra- variant PSEs in moderate yields. The first total synthesis of di-substituted PSE, lapathoside D 1' has been achieved successfully in short and simple synthetic steps from sucrose 3 as an inexpensive starting material. Lapathoside D 1 and a set of selected synthesized PSEs were tested for in vitro cytotoxicity against human cervical epithelioid carcinoma (HeLa) cell lines. Most of the compounds exhibited significant antitumor activity with their IC(50) values ranging from 0.05 to 7.63 μM. The primary screening results indicated that PSEs might be valuable source for new potent anticancer drug candidates.

Caffeic acid phenethyl ester (CAPE) prevents methotrexate-induced hepatorenal oxidative injury in rats

OBJECTIVES

This study aimed to investigate the antioxidant and anti-inflammatory effects of caffeic acid phenethyl ester (CAPE) on the methotrexate (MTX)-induced hepatorenal oxidative damage in rats.

METHODS

Following a single dose of methotrexate (20 mg/kg), either vehicle (MTX group) or CAPE (10 µmol/kg, MTX + CAPE group) was administered for five days. In other rats, vehicle (control group) or CAPE was injected for five days, following a single dose of saline injection. After decapitation of the rats, trunk blood was obtained, and the liver and kidney tissues were removed for histological examination and for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels and myeloperoxidase (MPO) and sodium potassium-adenosine triphosphatase (Na(+)/K(+) -ATPase) activity. TNF-α and IL-1β levels were measured in the blood.

KEY FINDINGS

Methotrexate administration increased the tissue MDA levels, MPO activity and decreased GSH levels and Na(+)/K(+) -ATPase activity, while these alterations were reversed in the CAPE-treated MTX group. Elevated TNF-α and IL-1β levels were also reduced with CAPE treatment.

CONCLUSIONS

The results of this study revealed that CAPE, through its anti-inflammatory and antioxidant actions, alleviates methotrexate-induced oxidative damage, which suggests that CAPE may be of therapeutic benefit when used with methotrexate.

Cancer chemoprevention mechanisms mediated through the Keap1-Nrf2 pathway

The cap'n'collar (CNC) bZIP transcription factor Nrf2 controls expression of genes for antioxidant enzymes, metal-binding proteins, drug-metabolising enzymes, drug transporters, and molecular chaperones. Many chemicals that protect against carcinogenesis induce Nrf2-target genes. These compounds are all thiol-reactive and stimulate an adaptive response to redox stress in cells. Such agents induce the expression of genes that posses an antioxidant response element (ARE) in their regulatory regions. Under normal homeostatic conditions, Nrf2 activity is restricted through a Keap1-dependent ubiquitylation by Cul3-Rbx1, which targets the CNC-bZIP transcription factor for proteasomal degradation. However, as the substrate adaptor function of Keap1 is redox-sensitive, Nrf2 protein evades ubiquitylation by Cul3-Rbx1 when cells are treated with chemopreventive agents. As a consequence, Nrf2 accumulates in the nucleus where it heterodimerizes with small Maf proteins and transactivates genes regulated through an ARE. In this review, we describe synthetic compounds and phytochemicals from edible plants that induce Nrf2-target genes. We also discuss evidence for the existence of different classes of ARE (a 16-bp 5'-TMAnnRTGABnnnGCR-3' versus an 11-bp 5'-RTGABnnnGCR-3', with or without the embedded activator protein 1-binding site 5'-TGASTCA-3'), species differences in the ARE-gene battery, and the identity of critical Cys residues in Keap1 required for de-repression of Nrf2 by chemopreventive agents.

Protective effects of caffeic acid phenethyl ester on iron-induced liver damage in rats

Caffeic acid phenethyl ester (CAPE) is a natural product with potent anti-inflammatory, antitumor, and antioxidant activities, and attenuates inflammation and lipid peroxidation. The purpose of the present study was to investigate the effects of CAPE on iron-induced liver damage. Rats were divided into four groups and treated for 7 days with saline (control group), 10 micromol kg CAPE/day s.c. (CAPE group), 50 mg iron-dextran/kg i.p. (IRON group) and CAPE and iron at the same time (IRON+CAPE group). Seven days later, rats were killed and the livers were excised for biochemical analysis. The administration of IRON alone resulted in higher myeloperoxidase (MPO) activity and lipid peroxidation than in the control and CAPE treatment prevented the increase in MPO activity and malondialdeyde (MDA) level. No differences were observed in all four groups with regards to superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities. Our results collectively suggest that CAPE may be an available agent to protect the liver from injury via inhibition of MPO activity.

Inhibitory effect of caffeic acid phenethyl ester on mice bearing tumor involving angiostatic and apoptotic activities

This study aims at investigating the anti-tumor effect of caffeic acid phenethyl ester (CAPE) against animal carcinogenesis. In order to substantiate this fact implanted tumor Ehrlich carcinoma cells were assessed in vivo to Swiss mice strain. We found that administrating of CAPE (15 mg/kg S.C.) showed that the tumor volume decreased significantly by 51%. As a result, it improved animal chances of survival and they became healthier. An anti-angiogenic effect of CAPE in vivo was observed, as determined by a significant serum matrix metalloproteinase (MMP-9) reduction (142.1 ng/ml), activation of endostatin serum level (1.9 ng/ml), as well as DNA fragmentation in tumor treated mice when compared with untreated ones.

CONCLUSION

CAPE has a significant inhibitory effect on tumor in vivo. This inhibition may be related to its angiostatic and apoptotic effects. It also reduced angiogenic factors which may shift the equilibrium to the angiostatic effect of CAPE. These findings provide the possibility for the future use of CAPE as tumor therapy in human clinical trials.

Protective effect of caffeic acid phenethyl ester on cyclosporine A-induced nephrotoxicity in rats

INTRODUCTION

Cyclosporine A, an immunosuppressive agent, is widely used after organ transplantation such as the liver and kidney. However, its widespread use is restricted because it has serious toxic effects on the kidney. Caffeic acid phenethyl ester (CAPE) is a natural product with potent anti-inflammatory, antitumor, and antioxidant activities, and it attenuates inflammation and lipid peroxidation induced by ischemia-reperfusion injury. The purpose of the present study was to investigate the effects of CAPE on cyclosporine A (CsA)-induced nephrotoxicity.

MATERIAL AND METHODS

Rats were divided into four groups and treated with saline, CAPE, CsA, and CsA + CAPE. Control rats were given saline; the CAPE group was given CAPE (10 micromol/kg/day) for 11 days intraperitoneally; the CsA group was given CsA (15 mg/kg/day) for 10 days subcutaneously; and the CsA+CAPE group was given CAPE for 11 days, and rats were s.c. injected with CsA in 0.5 ml of saline once a day for 10 days at the same time.

RESULTS

The administration of CsA alone resulted in higher myeloperoxidase (MPO) activity, lipid peroxidation, superoxide dismutase (SOD), and catalase (CAT) than in the control. The enzyme activities except CAT in rats treated with CAPE alone were not changed. CAPE treatment prevented the increase in malondialdehyde (MDA) and increased CAT activity more, but did not affect the activities of MPO and SOD enzymes.

DISCUSSION

CsA causes renal injury and CAPE prevents CAT- and lipid peroxidation-mediated nephrotoxicity via inhibition of oxidative process.

Plant phenolics regulate neoplastic cell growth and survival: a quantitative structure-activity and biochemical analysis

The anti-tumour activities of many plant phenolics at high concentrations (>100 micromol/L) suggest their potential use as dietary supplements in cancer chemoprevention and cancer chemotherapy. However, it is not clear what impact phenolic compounds have at the physiological concentrations obtained through consumption of high phenolic diets on neoplastic cells. In the present study, 54 naturally occurring phenolics were evaluated at physiologically relevant concentrations for their capacity to alter PC12 cell viability in response to serum deprivation, the chemotherepeutic agent etoposide, and the apoptogen C2-ceramide. Surprisingly, novel mitogenic, cytoprotective, and antiapoptotic activities were detected. Quantitative structure-activity relationship modelling indicated that many of these activities could be predicted by compound lipophilicity, steric bulk, and (or) antioxidant capacity, with the exception of inhibition of ceramide-induced apoptosis. Where quantitative structure-activity relationship analysis was insufficient, biochemical assessment demonstrated that the benzoate orsellinic acid blocked downstream caspase-12 activation following ceramide challenge. These findings demonstrate substantive mitogenic, cytoprotective, and antiapoptotic biological activities of plant phenolics on neoplastic cells at physiologically relevant dietary concentrations that should be considered in chemopreventive and chemotherapeutic strategies.