Limonoids as an effective Anticancer Agent: A Review

 

Neha O. Mankar, Yogita R. Mandlik, Chandrashekhar B. Chauriya

Ravi Institute of Diploma in Pharmacy, Mahadula, Koradi, Nagpur.

 

ABSTRACT:

Citrus limonoids (CLs) are a group of highly oxygenated terpenoid found mostly in the seeds, fruits and peel tissues of citrus fruits such as lemons, limes, pumellos, oranges, grapefruits, bergamots, and mandarins. [10] The term limonoids was derived from limonin, which is the first tetranortriterpenoid obtained from bitter principles of citrus [6]. CLs are found as both free aglycones and corresponding -D glucosides, the former mostly occurring in seeds while the latter are formed during fruit maturation. Conversion of agycon to glycon is carried out by two enzymes, uridine diphosphoglucose- limonoid glycosyl t ransferase and limonoid D-ring lactone hydrolase. [8,9]. Glucosides have an open D ring to accommodate an attached glucose moiety; in aglycones the D-ring is closed [9] Citrus fruits are particularly high in a class of phytochemicals known as the limonoids1and recent research suggests that limonoids appearto possess substantial anticancer activity. [7] The present review focused on pharmacological studies of citrus limonoids as an anticancer agent.

 

 

 

INTRODUCTION:

Cancer is abnormal growth of cells that starts to grow and propagate through uncontrolled cell division and gradually expand throughout body and finally lead to death by invading and destroying normal cells of body. Cancer treatments such as radiotherapy and chemotherapy can cause some complications. Worldwide effects are ongoing to identify new anticancer compounds from plants. From ancient time medicinal plants are potent natural sources of drugs to treat different human inflammations.

 

Citrus is one of the important fruits of high medicinal value and have long been the basis of commonly used traditional medicines in several Asian countries. Citrus fruits rich in Vitamin C and contain a range of key nutrients such as, vitamin A, carotenes of various kinds as well as many non-nutrient phytochemicals including classes of flavonoids, glucarates, coumarins, monoterpenes, triterpenes and phenolic acids⁹. Among these unique and less studied are the limonoid glucosides, a class of furan-containing triterpenes found mainly in the Rutacaeae and Meliacease families of fruits and that differ from flavonoids in chemical structure⁵. Limonoids are highly oxygenated, modified terpenoids with a prototypical structure either containing or derived from a precursor with a 4,4,8-trimethyl-17-furanylsteroid skeleton. All naturally occurring citrus limonoids contain a furan ring attached to the D-ring, at C-17, as well as oxygen containing functional groups at C-3, C-4, C-7, C-16 and C-17⁶. Citrus fruit tissues and byproducts of juice processing such as peels and molasses are Sources of limonoid glucosides¹⁵.

Limonoids possess antioxidant, antimicrobial, anticancer, antiviral, antiinflammatory, and other pharmacological activities in humans. Many compounds belonging to this group exhibit cytotoxicity to cancer cells, which draws scientists’ great attention due to their antineoplastic activity⁶. Upto now, most of the evidence for the protective effect of citrus against risk of cancer has come from case–control studies, and studies showed that of citrus fruit intake is associated with a reduced risk of multiple types of cancer, including cancer of the digestive tract, respiratory tract, pancreatic cancer, breast cancer, prostate cancer, nasopharyngeal cancer and cutaneous melanoma⁴.

 

Most recently several limonoid aglycones and a mixture of limonoid glucosides were administered in vitro to estrogen dependent and estrogen independent human breast cancer cell lines. The results of this study showed that the limonoids were equally potent as tamoxifen. for inhibiting the proliferation of estrogendependent breast cancer cells, and more potent than tamoxifen for activity against estrogen-independent cancer cells. It may be that the ability of limonoids in combination with flavonoids or tocotrienols, to inhibit tumor cell proliferation, to inhibit the metastatic spread of tumor cells or to preventimmuno-Suppression and toxicity induced by chemothera peutic agents, contributes to their effectiveness in the prevention and treatment of neoplastic diseases³.

 

According to recent pharmaceutical research and development for treatment of ca diseasees study it is found that Nano particlesformulation of Nim may help in delivery to cancer cells, sustained release, enhanced pharmacological activity, and decreased toxicity of the moiety¹³

 

CHEMISTRY-structure:

Citrus fruits and its closely related genera contain about 36 limonoid aglycones and 17 limonoid glucosides. Limonin glucoside is the most abundant of the limonoid glucosides in citrus. Azadirachta indica (Neem tree) a species of meliaceae family is a storehouse of limonoids containing more than 100 different limonoids and their derivatives in its different plant parts.⁶ Over 50 limonoids present in the Rutaceae and Meliaceae families have been isolated and identified. Each of these chemicals is a highly oxidized triterpene containing a furan ring. Additional double bonds are found throughout the multiring structures. The structural similarities between limonoids and kahweol led to research on the cancer chemopreventive activity of these citrus chemicals.² CLs are found both free aglycon and corresponding β-D-glucosides. The former mostly occurring in seeds, while the latter mostly formed during maturation of fruit.¹¹

 

Structure of Limonoid

 

Preparation of Limonoid Glucosides and Aglycones:

From Monterrey, Mexico, Orange seeds were obtained in bulk quantity then finely powdered before solvent extraction. Molasses of oranges and grapefruits were collected separately and stored at 4°C in 0.2% sodium azide. Limonoid glucosides were purified as described previously with the exception that naringin, the major flavonoidin molasses, was precipitated first by adjusting the pH to 3.5 and storing the product at 4°C overnight. Removal of naringin facilitated all subsequent purification steps. Individual limonoids were separated using preparative High-performance liquid chromatography (HPLC; Prep Nova-Pak C18 30 × 300 mm column, 950/1150 psi radial/back pressure, Waters Corp, Milford, MA), and purity, as determined by analytical HPLC, exceeded 95% for individual isolates.

 

Limonoid Aglycones were prepared from finely powdered seeds that had been extracted with hexane in a Soxhlet apparatus for 24 h at 60°C. Acetone extraction (60°C, 12 h) was used to obtain a crude aglycone mixture which was rotoevaporated and dried. Limonin, the major aglycone, was crystallized from the dried acetone extract with the addition of dichloromethane (1:2, wt/vol). The crystals were surface washed three times with isopropanol to remove traces of impurities to obtain pure crystals of limonin. Deacetylnomilin, nomilin, and obacunone were isolated from the filtrate of a silica column using a stepwise (20–80%) gradient of ethylacetate-hexane. Ultimately, alllimonoid aglycones used in the study were obtained as crystalline compounds with purities approaching 100% (Nova-Pak RP-18, 8 × 40mm column, UV 6000LP detector at 210 nm; Waters Corp.). Glucosides and aglycones were further characterized using liquid chromatography-mass spectroscopy negative-ionization mode as reported previously⁸.

 

Various studies carried out for citrous limonoids as anticancer agent:

Since past several years, various studies has been carried out throughout the globe for the treatment of cancer using citrus liminoids. Many experimental evidences have disclosed that citrus fruits containing limonoids and fruit juice have cancer chemopreventive property, limonoids have been shown to inhibit the growth of various cancer such as: human breast cancer cells in culture, neuroblastoma, lung, colon, oral and skin cancer etc.

In past study it was found that limonoids inhibit the growth of estrogen receptor-negative and -positive human breast cancer cells in culture, also it have been found that neuroblastoma cells get target and stop by limonoids. Hesperidin, other flavonoids, limonin 17-beta-D-glucopyranoside, and other limonoid glucosides are potential chemopreventive agents in orange juice that could account for the decreased colon tumor-genesis associated with feeding orange juice The citrus limonoids obacunone, limonin, nomilin and their glucosides and some aglycones inhibit chemically induced carcinogenesis and a series of human cancer cell lines, with remarkable cytotoxicity against lung, colon, oral and skin cancer in animal test system and human breast cancer cells. Nutritional research on health benefits of chemicals present in plant foods recommend that citrus limonoids possess substantial anticancer activity and they are also free of any toxic effects in animal models. Amit et.el (2006)⁶.

 

Citrus limonoid glucosides were suggested to have free radical–scavenging and apoptosis-inducing properties against certain types of cancers. Four highly purified limonoid glucosides,, obacunone 17_ D-glucopyranoside (OG), nomilinic acid 17_ D-glucopyranoside (NAG), limoin 17_ D-glucopypranoside (LG) and deacetylnomilinic acid 17_ D-glucopyranoside (DNAG) were tested for cytotoxic action and superoxide radical (O2_)-quenching activity against undifferentiated human SH-SY5Y neuroblastoma cells in culture and it was found that citrus limonoid glucosides are toxic to SH-SY5Y cancer cells and limonoid glucosides were capable of causing apoptosis. Poulose et.al (2005)⁵. Poulose et.al (2009)⁸, added various evidence for the citrus limonoids and their anticancer properties of and supports the argument that limonoid molecules with an open D ring are more likely to be the active form in vivo.

 

Edward et.al(2004)⁴, suggested that some citrus limonoids can inhibit the development of 7,12-dimethylbenz[a]anthracene-induced oral tumors. Also changes in the D ring of the limonoid nucleus can be tolerated without any apparent loss of biological activity.

 

last few years, many studies from a number of laboratories have concentrated on the anticancer activities of citrus limonoids. Inhibition of proliferation of colon cancer cells and neuroblastoma by four limonoids of citrus has been reported (Poulose et al., 2005)⁵ Studies have also shown that apoptosis is the major cause for inhibition of proliferation of colon cancer cells by citrus limonoids. The antiproliferative effects of limonoids have been shown in various cancers including breast cancer, colon cancer and stomach cancer and neuroblastoma cancer. Researchers were able to demonstrate that certain limonoids have antiproliferative and caspase mediated apoptosis inducing effects on human cancer cells in vitro (Gyawali et al., 2014)⁹.

 

Patel et al (2018)¹², found that the limonoid, nimbolide from nim (A. indica) suppresses the colorectal cancer in preclinical models by modulating pro inflammatory pathways Josephraj et al (2018)¹³ investigated the effectiveness of nimbolide, a neem limonoid in oral cancer which acts by inhibiting cytoprotectetive autophagy to activate apoptosis via modulation of PI3K/ATK/GSK-3β signalling pathway Patra et.al (2019)¹⁴ reveal the studies related targeted delivery of nim. Invitro study shows that nanodelivery of nim limonoid nimbolide found more effective in brest and pancreatic cell lines.

 

CONCLUSION:

Limonoids are tetranortriterpenoid with bitter principle having anticancer activity. along with it has also anti-malarial, antimicrobial, antiviral activity. No ill effect reported found on a high dose of limonine glucoside. In future nanoparticals of limonoids may be a promisable therapy for breast cancer and pancreatic cancer.

 

REFERENCES:

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12.   Patel M, Tripathy S, Mukhopadhyay K, Wangjam T, Cabang A, Morris J, and Wargovich M.; 2018, A Supercritical CO2 Extract of Neem Leaf (A. indica) and its Bioactive Liminoid, Nimbolide, Suppresses Colon Cancer in Preclinical Models by Modulating Pro-inflammatory Pathways DOI 10.1002/mc.22832

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15.   United state patent 29 may 2001 patent no.US 6, 239, 114, B1

 

 

Received on 26.12.2020          Modified on 16.01.2021

Accepted on 29.01.2021       ©A&V Publications All right reserved