Propolis A Honey Bee Product

Published Date: 02 Nov 2017

Keywords: antioxidant, chemistry, caffeic acid phenethyl ester (CAPE), ischemia/reperfusion (I/R)

Introduction:

Natural products played an important role in the process of drug discovery. Polyphenolics comprise an important category of bioactive compounds of natural origin. Propolis, is a naturopathic formula produced by honey bees (Apis mellifera L.) that is rich in polyphenolic compounds [1]. This resinous substance is used safely in folk medicine for its therapeutic benefits [1]. CAPE is considered the most extensively investigated constituent of propolis. Several studies elucidated that CAPE has a wide spectrum of biological properties. It has anti-inflammatory [2], antioxidant [3], and anticancer activities [4]. It is characterized by potent antioxidant and cytoprotective activities. CAPE has demonstrated protective effects against ischemia-reperfusion injury in multiple target tissues including brain, retina, heart, skeletal muscles, testis, ovaries, intestine, colon and liver. Several studies indicated the preventive effects of CAPE against chemotherapy-induced adverse drug reactions (ADRs) including several antibiotics (streptomycin, vancomycin, isoniazid, ethambutol) and chemotherapeutic agents (mitomycin, doxorubicin, cisplatin, methotrexate,). The present review discusses CAPE chemistry, and biological activities with special emphasis on antioxidant activity as well as protection against I/R injury and adverse drug reactions.

CAPE Chemistry:

CAPE is a diphenolic compound that has the empirical formula C17H16O4, and molecular weight of 284.3. The complete chemical name of CAPE is: (E)-3-(3,4-dihydroxyphenyl)-2-propionic acid, 2-phenylethyl 3-(3,4-dihydroxyphenyl)-2-propenoate [5-6]. The chemical structure of CAPE is shown in Fig.1. CAPE is a white, fine crystalline powder, insoluble in water but freely soluble in ethanol, methanol, acetone and DMSO. The solubility of CAPE in these solvents is about 10 mg/ml [5]. Alcohols should be carefully used in vivo as solvents for CAPE, since they can give rise to new bioactive caffeic acid esters through transestrification [7]. The recommended storage temperature for CAPE is -20ºC. CAPE was first identified as a component of propolis in 1987[8]. Propolis (bee glue) is a natural resinous hive product gathered by honeybees from buds, leaf and exudates of certain trees and plants. The chemical composition of propolis and its biological properties depend on the vegetation in the area from which they were collected [9]. Regardless of the source of propolis, CAPE is one of the most investigated and precious components of propolis. CAPE can be either extracted from propolis by different extraction methods or it can be chemically synthesized by several methods including response surface methodology from caffeic acid and phenethyl alcohols with a molar conversion value of 96% [10] and 91.2%.[11]. Its analogs such as 2-cyclohexylethyl caffeate and 3-cyclohexylpropyl caffeate can be synthesized from transesterification of methyl caffeate with Candida antarctica lipase B by using an ionic liquid, 1-butyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide, as a solvent [12].

Antioxidant activity of CAPE

Oxygen is utilized by the cells as a source of energy through oxidative phosphorylation. In this process, ATP generation is coupled with a reaction in which four electrons and four protons are added to O2 to form two molecules of H2O. But when a molecule of O2 gains only one electron to form superoxide anion (O2•–), this highly reactive oxygen species (ROS) tends to gain three more electrons and four protons to form H2O. This process involves several reactions and results in the production of other ROS such as hydrogen peroxide (H2O2), hydroxyl radical (OH•) and peroxynitrite (ONOO–). Although the controlled production of ROS has an important physiological role, a high production of ROS that is not counterbalanced by the cellular antioxidant defense produces oxidative stress. Oxidative stress has been proposed to play an important role in the pathogenesis of many diseases including cancer, cardiovascular disease, atherosclerosis, hypertension, ischemia/reperfusion (I/R) injury, diabetes mellitus, neurodegenerative disorders (Alzheimer’s disease and Parkinson’s disease), rheumatoid arthritis, and ageing [27, 28]. Accordingly, antioxidants may play a significant protective role in various disease conditions.

The antioxidant properties of polyphenols are widely acknowledged. CAPE is a hydroxyl derivative of cinnamic acid. The presence of CH2=CH-COOH group in cinnamic acids ensures greater antioxidant capacity compared to other phenolic acids as benzoic acid. The steric hinderance of the phenolic hydroxyls by a neighbouring inert group such as methyl enhanced its antioxidant activity [13]. Diphenolics have been shown to interfere not only with the propagation reaction [14-15] but also with the formation of free radicals, either by chelating the transition metal [16] or by inhibiting the enzymes involved in the initiation reaction [14-15]. Propolis extract exhibits interesting antioxidant properties. Russo et al. showed that propolis extract (containing CAPE) exhibited more prominent antioxidant properties compared to propolis deprived of CAPE [42]. This suggests an important role for CAPE in the antioxidant activity of propolis [42]. Consistent with this suggestion, CAPE showed potent ability to inhibit the formation of superoxide anion produced during autoxidation of β-mercaptoethanol and to quench 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. CAPE also inhibits xanthine oxidase (XO) activity [42-43], the well known physiological source of superoxide anions in eucaryotic cells. Moreover, CAPE exhibits a potent antilipoperoxidative [42], cytoprotective and antigenotoxic potential against oxidative damage [3, 17-19]. In 2012, Chen et al. showed that CAPE activated the expression of the antioxidant gene heme oxygenase-1(HO-1) and intercellular adhesion molecule 1 (ICAM-1) gene in retinal cells both in vitro and in vivo [20]. In this study, feeding CAPE to albino rats enhanced the electroretinographic responses and changed the lipid profile in the rats' retinas [20]. In a recent study, Sahin et al. (2013) indicated that CAPE treatment alleviated oxidative stress in acute methanol intoxication in the retina and optic nerve and preserved the integrity of the retinal ganglion cell layer as evidenced from histopathological evaluation [21]. Eşrefoğlu et al. (2012) reported that CAPE protects kidneys against aging-related oxidative injury in rats. The underlying mechanism was attributed to alleviation of malone dialdehyde (MDA) levels with concurrent elevation in superoxidae dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities, and reduced glutathione (GSH) levels in kidney tissues from old rats [22]. Moreover, Yilmaz et al. showed that CAPE protects against lipid peroxidation and replenishes the activities of antioxidant enzymes in the liver tissues of streptozotocin (STZ)-induced diabetic rat model [23]. STZ is used in experimental induction of diabetes and is known to produce oxidative stress in multiple target tissues. This protective capacity was supported by another study by Okutan et al. (2005), in which CAPE reversed the oxidative stress in cardiac tissues of STZ-induced diabetic rats [24]. Ozguner et al. (2005) elaborated that pretreatment with CAPE can provide significant protection against extracorporeal shock wave lithotripsy-induced free radical damage of renal tissues [25]. The antioxidant activity of CAPE was believed to protect against lithium-induced oxidative damage in renal tissues in rats [26]. In a recent study, in 2012, Mansour et al. demonstrated that 7 days pretreatment with CAPE protected against radiation-induced cardiac tissue damage in rats through reduction of MDA, adenosine deaminase (ADA) and XO activities together with boosting NOx level and SOD activity [27]. Different oxidative-stress targets affected by CAPE are illustrated in Fig. 2

Protective effect of CAPE against ischemia/reperfusion (I/R) injury

Several studies indicated that CAPE plays an important protective role against I/R injury in multiple tissue types including intestine, colon, retina, heart, ovaries, skeletal muscles, liver, brain and testis. These studies are summarized in Table 1 and Fig. 3. It was demonstrated by Teke et al. (2012) that CAPE alleviates the intestinal mucosal injury triggered by superior mesenteric I/R in rats. This was evidenced through improved intestinal mucosal injury scores, intestinal edema, reduced oxidative stress in the intestinal tissues and pro-inflammatory cytokine in plasma. CAPE also boosted the antioxidant parameters in the intestinal tissues. This enhanced the survival rate of CAPE-treated I/R animals [28]. This observation was further substantiated in another study by Teke et al. (2013) in which CAPE treatment prevented remote I/R injury-induced delay of colonic anastomotic wound healing [29]. Administration of CAPE reduced oxidative stress markers in colonic anastomotic tissues and plasma pro-inflammatory cytokine levels with subsequent improvement of colonic anastomotic bursting pressures and histopathological scores [29]. Shi et al. (2010) demonstrated the protective effect of CAPE against I/R-induced retinal injury in rats. This was attributed to the enhancement of the activities of the antioxidant enzymes SOD, GPx, and CAT in the retina of CAPE-treated animals. CAPE also, attenuated I/R-induced apoptosis of retinal cells in the inner nuclear and ganglion cells of the retina [30]. In a different study, it was shown that supplementing the cardioplegic solutions with CAPE improved the antioxidant defense system of rat heart during I/R injury. The groups treated with CAPE-supplemented solution showed significant reduction in MPO, Na+/K+ ATPase activity [31]. In 2009, Kart et al. showed that CAPE ameliorated ovarian I/R damages in rabbits through its antioxidant activity. CAPE prominently reduced the degenerative effects of I/R injury as evidenced by histopathological assessment [32]. CAPE also, exhibited comparable effects to vitamin E in protecting against the harmful effects of hind limb I/R in skeletal muscle [33]. The possible protective mechanisms of CAPE were explored in a separate study by Andrade-Silva et al. in 2009. The group concluded that CAPE effect may be related to its inhibition of the NF-kB signaling pathway and decreased tissue inflammatory response following skeletal muscle I/R [34]. Saavedra-Lopes et al. (2008) showed that the same mechanism is involved in CAPE amelioration of the acute inflammatory response following I/R in the liver [35]. In 2008, Feng et al. reported that CAPE compensates the functional alterations in mitochondria isolated from mouse brain and liver tissues challenged by anoxia-reoxygenation. This was attributed to inhibiting the decrease in membranes fluidity, as well as the increase in lipoperoxidation and protein carbonylation. This is in addition to the blockade of the enhanced release of cardiolipin and cytochrome c [36]. CAPE was also reported to provide neuroprotection against cerebral I/R through attenuating the elevation of plasma MDA, CAT and XO content and restoring the levels of plasma GSH and NO [37]. CAPE was also reported to protect the testis against I/R injury [38]. It attenuated testicular tissue damage, MPO levels as well as iNOS activity in testicular tissues [38]. In another study, in 2009, Namazi et al. suggested that the major mechanism for CAPE protective effect against ischemia-reperfusion injury is via decreased expression of lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1(ICAM-1) [39]. Further clinical studies are required to clarify the potential merit of CAPE I/R-induced organ injury that may be encountered during particular surgeries or with disease conditions as myocardial infarction and stroke.

Preventive effects of CAPE against drug adverse reactions

There is no doubt that the adverse reactions encountered with chemotherapies are major limiting factors for their use. Development of solutions to minimize such toxic effects is a critical issue. Several studies suggested the potential merit of CAPE as a chemopreventive agent against the toxic effects of a wide range of commonly used chemotherapeutic agents. Table 2 summarizes these studies. Sulaiman et al. (2012) reported that CAPE protects against mitomycin-induced clastogenesis. It significantly decreased the number of chromosomal aberrations, micronuclei and adapted the mitotic activity reduction in the bone marrow cells of mice triggered by mitomycin. This was attributed, at least in part, to CAPE antioxidant effects [40]. Recently, Bakir et al. (2013) showed that CAPE treatment attenuated streptomycin-induced injury and apoptosis in the inner ear hair cells. The effect was confirmed through histopathological and immunohistochemical examination of cochleas as well as distortion product otoacoustic emissions testing [41]. Ocak et al. (2007) indicated that CAPE protects against vancomycin-induced alterations in kidney function and histology through counteracting the elevation in MDA and NO levels in kidney tissues [42]. Sahin et al. (2013) demonstrated that CAPE treatment was able to decrease the oxidative stress in the retina and optic nerve in isoniazid and ethambutol-treated rats and to prevent the shedding of retinal ganglion cell (RGC). Its interaction with SOD seems crucial for alleviation of ocular oxidative stress and RGCs toxicity [43]. Doxorubicin (DOX) is one of the most important chemotherapies against solid tumors. However, its use is limited by dose-related toxicities in different target tissues. It was indicated by Yagmurca et al. that pretreatment of rats with CAPE protected renal tissues against DOX-induced toxic damages. The nephrotoxic action of DOX is attributed to free radical generation which is attenuated by CAPE antioxidant effect [44]. DOX may also induce cardiotoxicity due to the same mechanism of free radical generation. Chlopcikova et al. reported that caffeic acid, the main metabolite of CAPE [7] is an effective cytoprotective agent against DOX-induced cardiotoxicity in rats [45]. Fadillioglu et al. indicated that the protective effect of CAPE against DOX- induced cardiotoxicity in rats occurs via ameliorating the changes in oxidant–antioxidant status of heart tissue. This is in addition to reversing the changes in haemodynamics, biochemical parameters, and ultrastructural alterations [46]. Lin et al. demonstrated that CAPE attenuates DOX-induced neuronal injury through its antioxidant properties [47].

Cisplatin is an anticancer alkylating agent that is basically effective for germ cell tumors. However, its use is limited by dose-related nephrotoxicity. Several studies showed that pretreatment with CAPE abolished cisplatin-induced nephrotoxicity in rats as evidenced by compensating the alterations in BUN, creatinine, NO, CAT, SOD, GPx, MPO and by histopathology [48-49]. In another study, Yilmaz et al. (2010) indicated that CAPE significantly decreased the total number of chromosomal aberrations and abnormal metaphases induced by cisplatin [50]. This was attributed to the free radical scavenging effect of CAPE. Iraz et al. (2006) reported that CAPE could prevent cisplatin-induced oxidative changes in the liver via boosting the antioxidant defense system and reducing ROS [51]. Previous reports suggested a protective role of CAPE against MTX-induced hepatorenal injury in rats [52-53]. This was explained by the ability of CAPE to significantly reduce TNF-α and IL-1β levels in serum in addition to protecting against lipid peroxidation. In a recent study, Cakir et al. (2011) suggested that GSH levels and Na+K+-ATPase activities in hepatic and renal tissues were restored upon administration of CAPE, showing the protective effect of CAPE on membranes and other subcellular colloidal compartments [53]. Furthermore, CAPE was shown to protect against cisplatin-ototoxicity in rats via minimizing the disturbance in XO/xanthine dehydrogenase (XD) system [54]. XD and XO catalyze the same reaction at the end steps of the purine catabolic pathway. XD enzyme may be converted to XO to produce more superoxide radicals during I/R and oxidizing environment. This pathway is involved in cisplatin-ototoxicity. Methotrexate is one of the most widely used antimetabolites in cancer chemotherapy. Several studies assessed the protective actions of CAPE against methotrexate (MTX)-induced toxic reactions. Moreover, Uzar et al. indicated that CAPE alleviated methotrexate (MTX)-induced alterations in adenosine deaminase (ADA) activity and NO levels that are involved in the pathogenesis of MTX-induced spinal cord toxicity [55]. It was also reported that CAPE acts as a potential protective agent against cerebellar-oxidative damage induced by MTX via its antioxidant properties [56]. Studies by, Armagan et al. (2008) indicated that CAPE protects against MTX-induced testicular toxicity [57].

Conclusions

CAPE is a polyphenolic component of propolis that is characterized by multiple biological activities. This review addresses the up to date studies about CAPE potential antioxidant and cytoprotective activities as well as protection against I/R injury and adverse drug reactions. CAPE is characterized by potent antioxidant and cytoprotective activities. CAPE has demonstrated protective effects against ischemia reperfusion injury in multiple target tissues including brain, retina, heart, skeletal muscles, testis, ovaries, intestine, colon and liver. Several studies indicated the preventive effects of CAPE against chemotherapy-induced adverse drug reactions (ADRs) including several antibiotics (streptomycin, vancomycin, isoniazid, ethambutol) and chemotherapeutic agents (mitomycin, doxorubicin, cisplatin, methotrexate,). Overall, these data suggest the potential benefit of using CAPE as a dietary supplement to improve human health condition and counteract oxidative stress, ischemia reperfusion injury and adverse drug reactions. Further preclinical safety studies are needed to determine the therapeutic index of CAPE before its use in humans.