Anticancer of genus Syzygium: a systematic review

Aim: One in eight fatalities globally are considered cancer-related. The need for cancer therapy is growing. Natural products continue to play a role in drug development, as up to 50% of authorized drugs in the last 30 years have been isolated from natural sources. Methods: Anticancer, antioxidant, antibacterial, antifungal, antiviral, analgesic, anti-inflammatory, and other actions have all been reported in research papers using plants from the Syzygium genus in the treatment and prevention of disease. Results: Results from the anticancer test showed that the genus, especially Syzygium aqueum, Syzygium samarangense, and Syzygium cumini had significant promise as an anticancer agent in vitro against several cancer cell lines. Numerous factors, including phytochemical composition, increased apoptotic activity, decreased cell proliferation, stopped angiogenesis, and reduced inflammation. Conclusions: These results, despite preliminary, show promise for further purification and investigation of bioactive compounds and extracts within the genus Syzygium for their anticancer properties.


Introduction
Cancer is a group of diseases defined by the unchecked growth and spread of cells. Cancer is a major killer worldwide. In 2008, cancer was responsible for 7.6 million deaths worldwide, the vast majority of which occurred in low-income regions [1]. This number is expected to keep rising due to demographic shifts and the prevalence of risky lifestyle choices. Despite the widespread scientific evidence, many of us still don't know that poor dietary habits are a major cause of cancer [2]. Humans are more likely to develop cancer due to the high levels of chemicals, preservatives, and coloring agents in the food consumed regularly [2]. The inability of anticancer medications to discriminate between cancer cells and healthy cells, as well as the resistance of cancer cells to chemotherapeutic agents, are major factors in the failure of cancer treatment [3]. The need for cancer therapies is growing. Consequently, it is crucial and essential to look for novel compounds that can be used to cure various forms of cancer. Natural products continue to play a role in drug development, as up to 50% of authorized drugs in the last 30 years have been isolated from natural sources. Novel sources of bioactive chemicals in medicinal plants with promising anticancer potential. Syzygium belongs to the family Myrtaceae, which includes 3,800-5,800 different species and 140 different genera. Syzygium, on the other hand, has 1,100-1,200 species and is found primarily in tropical and subtropical regions of the world, making it the biggest woody genus of flowering plants [4]. Some Syzygium species are currently enjoying a boom in popularity in domestic and foreign markets in addition to their centuries-long use as spices, food preservers, and medicinal herbs. A wide range of biological activity have been reported in research papers using plants from the Syzygium genus in the treatment and prevention of disease [5][6][7][8]. In our search for information, we were unable to locate up-to-date analysis of the effectiveness of genus Syzygium against cancer. Not many reviews have been done on the genus as a whole with regard to cancer except [9]. Therefore, this systematic review discussed in detail the great potential for obtaining the lead drug from chemical constituents of various species from the genus Syzygium as the anticancer.

Exclusion criteria
We did not include information from sketchy websites in our analysis. None of the articles were considered since they were written in a language other than English, and this includes thesis papers and reviews.

Taxonomy, origin, and distribution of genus Syzygium
Aroma, essential oil, flower composition, plant structure, and phloem distribution are only a few of the characteristics used to categorize members of the Myrtaceae family [10]. In 1893, the Myrtaceae were divided into two groups, the Leptospermoideae and the Myrtoideae, based on whether the plants had opposite or alternate leaves and capsular or fleshy fruits [4]. In 1984, it is argued that the taxonomic classification of the family Myrtaceae should be based on the morphological features of the species within the family, and they validated their arguments with molecular studies, which led them to the conclusion that there are only two families and seventeen tribes: the Psiloxyloideae and the Myrtoideae [11]. The family Myrtaceae has been found to have numerous species and a great deal of genus variety. In the family Myrtaceae, the Syzygieae tribe accounts for most of the species. The genera Syzygium and Psidium, followed by Eugenia, are the most widely planted in the family Myrtaceae. Syzygium has 1,200-1,500 species, Eugenia has about 1,150, and Eucalyptus has around 700 [10]. The complexity and difficulty of taxonomic identification can be traced back to the family's high level of species diversity. Numerous genera within this family have attracted attention for their potential commercial value since their medical and industrial applications have been recognized the world over. Syzygium is a vast family of plants that ranges from southern India and southeast China to southeast Australia and New Zealand [12]. However, whereas Malaysia is the canter of the genus in terms of species richness, it appears that the Malaysian-Australian region is the canter of the genus in terms of its basic evolutionary diversity. Multiple species belong to this genus, which extends from southern East Asia and the Pacific to Africa and Madagascar [13]. They are extremely fragrant plants, and most of the species in this genus are used medicinally. Additionally, the fruits are taken fresh, and their flavour composition has demonstrated that they are also aromatic.

Traditional uses of some members of the genus Syzygium
Chemical, genetic, and molecular diversity are the most prominent types of plant variety, but there is also a great deal of species diversity and eco-climatic adaptations among plants across the globe. Humans from all walks of life and all corners of the globe have long relied on the healing properties of nature's plants, using them for anything from food to prescription drugs. In many parts of the world, people turn to plants as a complementary method of treating cancer. Those that are less harmful to healthy cells, have less of an adverse biological impact, and have evolved in tandem with their targets are preferred [3]. Syzygium aqueum is cultivated for its edible fruits, leaves, and bark. Fever, headaches, gastrointestinal issues, diabetes, high cholesterol, skin problems, and even some forms of cancer can all be alleviated by eating apples [14]. It's no secret that Syzygium aromaticum is a staple in Indian cooking [15]. Syzygium aromaticum is utilized as a warming and stimulating stimulant in both Indian and Chinese traditional medicine [16]. Syzygium aromaticum essential oil has long been used to treat burns and wounds, as well as a pain reliever in dental care, as well as to cure tooth infections and toothache [17]. It has been utilized by Ayurvedic doctors in India to treat respiratory and digestive disorders since ancient times, and recent scientific research has confirmed its efficacy as a chemo-preventive agent [15]. Sore throat, bronchitis, asthma, thirst, biliousness, diarrhea, and ulcers are only some of the conditions that can be alleviated by using Syzygium cumini bark [18]. Syzygium cumini leaf juice is administered alone or in combination with carminatives like cardamom and cinnamon to treat diarrhea in children [19], Syzygium cumini leaves, mango leaves, and myrobalan leaves are combined with goat's milk, honey, and carminatives like cardamom and cinnamon to treat dysentery with a bloody discharge [18]. Syzygium cumini has historically been used to treat a number of ailments, such as diabetes, inflammation, and diarrhea [20]. Syzygium jambolanum fruits are considered spleen disease-treating, tonic, astringent, and carminative [21]. Both pharyngitis and ringworm infections are alleviated with the use of the fruits and seeds of Syzygium jambolanum [21]. The fruits of Syzygium jambolanum have a sharp, sugary flavor and are also chilly, dry, and astringent to the digestive tract [21]. The plant Syzygium zeylanicum has a long history of usage in traditional medicine for conditions like fever, headaches, arthritis, and joint discomfort [22]. Malay people have historically utilized Syzygium polyanthun leaves and roots to manage and treat endometriosis, ulcers, hypertension, and diabetes [23]. In Africa, Syzygium guineense is used to treat malaria, stomach aches, and ringworm by applying the root, leaf, bark, or fruit [24,25]. For the creation of evidence-based medications, we give an overview of the traditional applications of a few selected Syzygium species. This genus has many species that are utilized in traditional medicine. Analysis of the criticism of these species in light of current knowledge of anticancer activity is crucial because it could eventually close the gap between conventional wisdom and evidence-based research.

Anticancer
In contrast, extracts from medicinal plants can be used to effectively suppress cancer cell malignancy without causing the harmful effects that come with chemotherapy drugs [26]. There has been a recent uptick in the investigation of medicinal plants for their potential anticancer effects due to the urgent need to discover new, safe, and effective therapeutic agents. The U.S. National Cancer Institute (NCI) states that a half maximal inhibitory concentration (IC 50 ) value of less than 20 µg/mL for crude extract and less than 4 µg/mL for purified chemicals is required for anticancer activity [3]. Ideal anticancer drugs target cancer cells alone, killing or crippling them while leaving healthy cells unharmed [27]. Modulating the cell cycle is getting a lot of interest because of the central role it plays in cancer progression. Herbs that have been shown to elicit cell cycle arrest have the potential as both cancer preventatives and therapeutics. Genus Syzygium was found to be active against several cancer diseases ( Figure 1 and Tables 1-7). Results from Syzygium aqueum demonstrated that both substances inhibited the proliferation of cancer cells, with arjunolic acid demonstrating the strongest activity against HeLa cell lines [28]. Fruit extract of Syzygium aqueum was found to have antiproliferative activity against MCF-7, a cell line that is highly dependent on the hormone estrogen, suggesting that a component in the extract is responsible for its cancer-fighting abilities. Plant polyphenols have been linked in multiple studies to a reduction in breast cancer metastasis [29].   -: not applicable  22 ----The relative IC 50 value of the ethanolic clove extract was 6.8 µg/mL, making it the most potent antiproliferative agent tested. [60] 23 ---Breast The accumulation of nanoparticles in the sub-G1 phase of the cell cycle after treatment with extract coated with polyvinylpyrrolidone (PVP) iron oxide nanoparticles and PVP iron oxide nanoparticles in MCF-7 cell lines confirmed the induction of apoptosis. [61] 24 Flower buds Ethanolic -Cervical Cell viability was found to decrease after treatment with the extract in a dose-and time-dependent manner, suggesting an antiproliferative action (P < 0.05). [62] 25 Flower Aqueous 50-1,000 ppm -LC 50 values of 227.1 g/mL showed that the extract is toxic to larvae. [63] -: not applicable    2 Leaves Aqueous --The cell cycle arrest of HB4C5 is induced by the crude extract between G1 and S phase. [83] 3 Ripened and unripe fruits, leaves Ethanol --Fruit and leaf extracts were found to be ineffective (LC 50 > 1,000 μg/mL). [84] -: not applicable   The aqueous extract of Syzygium samarangense at 100 µg/mL and 250 µg/mL stimulated the Nrf2-ARE pathway in human HepG2-C8 cells that had been transfected with stable ARE-luciferase plasmids. Additionally, TPA effectively prevented the transformation of mouse epidermal JB6 P+ cells, indicating that the extract may have some therapeutic potential (Table 2). Furthermore, according to a reported study [36], the extracts had an impact on cell viability that was both noticeable and concentration-dependent. A biological sign of intrinsic apoptotic cell death is ladder-shaped DNA fragments in a DNA fragmentation experiment. The extract's ability to cause apoptosis was demonstrated by morphological changes in cells that were treated with it. It is investigated that the human colon cancer cell line SW-480, and it was discovered that it was susceptible to their cytotoxic effects (IC 50 values of 10, 35, and 35 μmol/L, respectively) [37]. The family of chalcones includes the substances 2',4'-dihydroxy-3',5'-dimethyl-6'-methoxychalcone (1), 2',4'-dihydroxy-3'methyl-6'-methoxychalcone (stercurensin, 2), and 2',4'-dihydroxy-6'-methoxychalcone (cardamonin, 3). It is also concluded that when the Syzygium samarangense leaf extract was evaluated using the HeLa cell line, the IC 50 result was 40.5 μg/mL [41].
Syzygium aromaticum essential oil had the greatest cytotoxic effect in both the BSLT and MTT assays, followed by the ethanol and water extracts [2]. Essential oil in the 24-h BSLT had an LD 50 of 37 µg/mL. In addition, the essential oil's IC 50 values in 24 h of MTT assays were 36.43 µg/mL [2]. Oil extract of Syzygium aromaticum demonstrated the most cytotoxic activity out of the three types of extracts tested against five distinct cancer cell lines [15]. Morphological examination and 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) staining confirmed that cell disintegration and subsequent membrane rupture were the cause of cytotoxicity. Within 24 h, clove oil at 300 µL/mL caused the most cell death and apoptotic cell death in esophageal cancer cells [15]. Eugenol, which was found in Syzygium aromaticum, may induce apoptosis in order to kill certain cancer cells by exerting its cytotoxic effects [15]. The stem extract has a significant and selective cytotoxic effect on MCF-7 cells, with an IC 50 of 331.6 µg/mL [43]. The stem extract's cytotoxic effect was caused by the stimulation of cell death's apoptotic mechanism [43]. The eugenol isolated from Syzygium aromaticum was extremely inhibitive, with effects on cell viability that depended on time and dose as well as consistent morphological changes [44]. Apoptosis was detected by the IC 50 at 81.85% cell viability (Table 3) [44]. There was evidence of eugenol's activity in several other cancer cell lines, not just HeLa cells. Regarding promoting cell death, eugenol's action depends not only on the concentration but also on the dosage and length of exposure. The cell viability of the A-375 cancer cell line was decreased by at least 50% in the presence of both eugenol chitosan-based nanoparticles (EugChiNPs) and Syzugium aromaticum chitosan-based nanoparticles (SAChiNPs) at all concentrations examined [45]. Neither eugenol nor SAEO demonstrated any discernible cytotoxicity compared to the control group at doses of 150 μg/mL. Cell viability decreased to under 50% when eugenol and SAEO concentrations (> 600 μg/mL) were increased [45]. The powerful antioxidant, antiproliferative, and antibacterial effects of Syzygium aromaticum (clove) are attributed to its tannins, flavonol glycosides, and volatile phenolic oils (eugenol, acetyl eugenol). It is perfect for use as a cancer chemo preventive drug since it has qualities that make it antibacterial, antiseptic, and anti-inflammatory [50]. Eugenol may have an apoptotic effect by reducing cyclooxygenase-2 (COX-2), B-cell lymphoma, and interleukin-1 beta production, and by increasing the activity of caspase-3 and caspase-9 caspase proteins. Therefore, our results suggest that the natural compounds present in Syzygium aromaticum, especially eugenol, could be exploited to create a new treatment for esophageal, breast, and cervical cancer (Table 3).
Syzygium cumini extracts at 40% concentration inhibited HeLa and SiHa cell growth by 14.4% and 11.8%, respectively; at 80% concentration, the extract inhibited growth by 30.3% and 23.2% [64]. Growth of HT-29 cell lines was significantly inhibited by the Syzygium cumini extract [65]. After treatment, there was also a notable shift in the intended gene expression ratio (Bax:Bcl-2). The results of the DNA damage assay and the apoptotic process suggested by the healing of the wounds indicate that the likelihood of metastasis has decreased following treatment with Syzygium cumini extract [65]. Animals in groups V-VII given Syzygium cumini extract had higher levels of the non-enzymatic antioxidant protein glutathione (GSH) in their stomachs compared to controls given the carcinogen [66]. Syzygium cumini has been found to contain fatty oils, phytosterols, and phenolic compounds. Given the results of the current investigation, it is possible that all of these factors work together to endow this plant extract with its anti-cancer effects [66]. Gallic acid and quercetin extracted from Syzygium cumini fruits exhibit > 90% cytotoxic effects at modest concentrations [67]. Based on the results, the IC 50 of ethyl acetate, methanol, aqueous, and cisplatin (standard) was 330 µg/mL (moderately toxic), 378 µg/mL (moderately toxic), 360 µg/mL (not toxic), and 8.11 µg/mL (very toxic), respectively [3]. From these numbers, it's clear that the IC 50 value for the ethyl acetate extract is the lowest. The more toxicity there is, the lower the IC 50 value. Treatment with Syzygium cumini extract (SCE) significantly reduced the number of papillomas present (Table 4). In this study, rats given an oral dose of Syzygium cumini seed extract showed no signs of tumor growth over the course of the experiment [72]. While the ethanolic extract's LC 50 = 81 μg/mL of anticancer activity was higher than that of the other extract's (70.7%), it was still lower than the 91.71% and 100% inhibition seen with the pure compounds [b-sitosterol (LC 50 = 55.0 μg/mL and kaempferol 7-O-methylether, LC 50 = 48.0 μg/mL)] [73]. These results may be explained by the fact that many active components present in the crude extract of ethanol compete. Lung cancer cell viability was found to be considerably decreased by an extract of Syzygium cumini at the highest dose (2 mg/mL) [81]. This type of cancer is now thought to be the most frequent because of its large prevalence (millions of new cases annually) [81].
It is reported that a flavonoid fraction isolated from Syzygium polyanthum leaves is cytotoxic to mouse colon 26 adenocarcinoma cells and human hybridoma HB4C5 mice [83]. The extract exhibited a modest cytotoxic effect on 4T1 and MCF-7 cells, with IC 50 values of 672 µg/mL and 126 µg/mL, respectively ( Table 5). The active flavonoid component of Syzygium polyanthum stacked the cell cycle at G2/M phase, indicating that the effect of cell growth inhibition was not attributable to apoptosis [83].
When the extracts of Syzygium guineense were used at a concentration of 50 μg/mL, they fully inhibited the Wnt-dependent TopFlash transcription but had no effect on the constitutive CMV-Renilla transcription [85]. Thus, the active compound(s) from Syzygium guineense specifically block Wnt3a-induced β-catenin stabilization transcription in TNBC cells but have no effect on transcription in general [85]. GI 50 = 50 μg/mL was found to be an effective inhibitor of melanoma cell proliferation from stem extract [86].
After 24 h of treatment, the IC 50 values for HCT 116 and Pa-1 cell lines were 59.9 μg/mL and 47.5 μg/mL, respectively, indicating strong cytotoxic effects of the leaf essential oil of Syzygium myrtifolium compared to control. A higher dose of the essential oil greatly suppressed the expansion of HCT 116 and Pa-1 cell lines [13]. Essential leaf oil's cytotoxicity may result from the major and minor constituents' synergistic and cumulative actions of germacrene D, caryophyllene oxide, and caryophyllene.
Cell viability was reduced by 10% and 22% in MiaPaCa-2 and ASPC-1 pancreatic cancer cells, respectively, when treated with Syzygium paniculatum extract at 100 μg/mL, but human pancreatic ductal epithelial (HPDE) cells had no effect [93]. Conversely, MiaPaCa-2 and ASPC-1 cell viability were significantly decreased by 77% and 34%, respectively, after incubation with a higher dose of the extract (200 μg/mL, P = 0.0004 and P = 0.02, respectively). The results were compared to those achieved with gemcitabine, a chemotherapy drug often used as the initial line of defense against pancreatic cancer [93].
Cells treated with Syzygium mundagam bark extract were clearly smaller and had more nuclear damage in micrographs. This morphology of cell death was confirmed by Hoechst staining. Reduced ATP levels (47.96%) and elevated LDH levels (40.96%) in MCF-7 cells were indicative of SMBM-induced toxicity [94]. Shape loss, condensed nuclei, distributed nuclear granules, and shattered nuclei may have all contributed to the extract's potency. Apoptosis may explain the extract's observed nuclear damage [94]. There is an undeniable demand for less harmful and invasive treatment options for many cancer types. It is indicated that the natural cures Syzygium aromaticum, Syzygium aqueum, Syzygium samarangense, Syzygium cumini, and possibly all members of the genus Syzygium, inhibit the development of cancer cells by apoptosis and other processes (Table 7). Apparently, they have chemicals that may fight cancer. Some of the ways the compounds or extract prevent cancer progression include increased apoptotic activity, decreased cell proliferation, stopped angiogenesis, and reduced inflammation. The resveratrol molecule found in the Syzygium genus can reduce the number of terminal end buds. Resveratrol can also inhibit 5-lipoxygenase (5-LOX) and COX-2 activity.

Compounds responsible for anticancer in genus Syzygium
Plants have evolved over many millions of years to create a wide variety of compounds. Each of the several plant chemical groups from which phytochemicals are derived has its own special set of health advantages. Phytochemicals may in some cases shield people from a variety of ailments. Phytochemicals are plant compounds with anti-inflammatory or antioxidant activity but no nutritional value. Although plants create these phytochemicals as a form of defense, it is revealed that they also offer protection against human disease. There are many different phytochemicals found in plants, each with its own unique properties. Polyphenols, a large and varied chemical class consisting of diverse combinations and polymers of A, has been found to have powerful anticancer capacity and may even have protective benefits on human health. A variety of phytochemicals, including flavonoids, phenolics, and polyphenolic, are produced by plants; these compounds are powerful antioxidants and can reduce the negative effects of oxidative stress [74]. Numerous plant-based chemicals have been touted for their purported anticancer, anti-inflammatory, and antioxidant properties. Compounds found in plants have been shown to increase the absorption of a medicine used to prevent cancer cell growth in the digestive tract. The abundance of bioactive phytochemicals in plants like Syzygium species makes them a typical base of supplementary treatments. Syzygium species has been linked to numerous natural chemicals with anticancer properties, including phenolics, oleanolic acid, betulinic acid, and dimethyl cardamonins ( Figure 2). Terpenoids, chalcones, (-)-epigallocatechin, samarangensis A and B, pinocembrin, samarone A-D, jasmonic acid, lignans, alkyl phloroglucinols, hydrolyzable tannins, and other derivatives are all metabolites widely generated by plants in the Syzygium genus ( Figure 2). The bioactive components in fruits with strong antioxidant and anticancer activities are often polyphenols and their secondary metabolites like flavonoids and proanthocyanidins [93]. Some members of the Syzygium genus contain phytochemicals such as sesquiterpenes, monoterpenes, hydrocarbons, phenolic compounds, eugenol, and caryophyllene [63]. Eugenol inhibits the growth of colon, stomach, breast, prostate, melanoma, and leukemia cancers, whereas caryophyllene inhibits the growth of pancreatic, cutaneous, lymphatic, and cervical cancer [98]. Also, it is suggested that eugenol's anticancer effect was achieved by a combination of mechanisms, including induction of apoptosis, cell cycle arrest, and reduction of proliferation, migration, angiogenesis, and metastasis in a variety of cancer cell lines [63]. Concentration-dependently, arjunolic acid decreased the wound closure rate of PANC-1 cancer cells and triggered a cell-cycle arrest at G0/G1 [99]. Gallic acid controls cancer development and progression by modulating the expression of a number of genes involved in cell death and proliferation [100]. Pathways indicate the probable mechanisms of action that cause G2/M arrest and death in a wide range of cancer cells (Figure 2). G2/M arrest is caused by lowering cell division cycle protein 2 (cdc2), cdc25c, and cyclin B1 and boosting p21 WAF1/CIP1 [101]. Furthermore, it causes apoptosis by raising the Bax:B-cell lymphoma-extra-large (Bcl-xL) ratio, caspase 3 activity, and cleaved PARP while lowering pro-caspase proteins (caspase-3, -6, -8, and -9) [101]. In conclusion, there is great potential for the Syzygium genus to be developed as an anticancer agent in the future. Through this study, the genus's latent capabilities have been revealed. Considering these encouraging findings, the potential for a natural substance to play a central role in the next generation of cancer treatments is undeniable. To effectively treat cancer cells, we propose more studies with multidisciplinary directions.

Discussion
Drug discovery and the development of therapeutic medicines owe a great deal to natural goods, particularly medicinal plants. Many secondary metabolites with various biological or pharmacological effects can be found in the genus Syzygium. The information was collected and analysed from the research articles. Revealed members of the genus Syzygium are traditionally used in the treatment of cancer and based on the in vitro and few in vivo evaluations showed that all documented species are effective in the treatment of cancer especially Syzygium aqueum, Syzygium aromaticum, Syzygium cumini, and Syzygium samarangense are rich sources of phytochemical constituents. It is proved that Syzygium genus is a source of bioactivity in the Myrtaceae family. We can infer from this systematic review that members of the genus Syzygium preferentially suppress the proliferation of all types of cancer cells tested and has no effect on normal cells. The systematic review, therefore, recommends further studies in the following species in terms of clinical trials, effective dosage, toxicity, and actual mechanism of action of the plant extract or the isolated compounds. Drug development and discovery from the genus Syzygium necessitates multidisciplinary scientific study.

Conflicts of interest
The authors declare that they have no conflicts of interest.