Indan Journal of Medical Research Indan Journal of Medical Research Indan Journal of Medical Research Indan Journal of Medical Research
  Home About us Editorial board Search Ahead of print Current issue Archives Submit article Instructions Subscribe Contacts Login  
  Home Print this page Email this page Small font sizeDefault font sizeIncrease font size Users Online: 1903       

   Table of Contents      
ORIGINAL ARTICLE
Year : 2011  |  Volume : 134  |  Issue : 3  |  Page : 369-374

In vitro & in vivo estrogenic activity of glycoside fractions of Solanum nigrum fruit


1 Division of Plant Molecular Biology, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
2 Integrated Cancer Research Programme, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India

Date of Submission09-Feb-2010
Date of Web Publication30-Sep-2011

Correspondence Address:
S Manjula
Division of Plant Molecular Biology, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695 014
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


PMID: 21985821

Rights and PermissionsRights and Permissions
   Abstract 

Background & objectives: The mature fruits of Solanum nigrum contains steroidal glycosides. These are often used as vegetable and there are evidences on tribal use of these fruits as an oral contraceptive. The present study was carried out to evaluate the estrogenic potential of S. nigrum fruits by in vitro and in vivo assays.
Methods: Defatted methanol extract of dried S. nigrum fruits was column fractionated and the glycoside positive fractions pooled. Definite concentrations of the fraction were used for in vitro and in vivo assays. The effect on cell viability was analyzed in MCF-7 cell lines by MTT assay followed by in vitro evaluation of estrogenicity by hydroxy apatite (HAP) binding assay. The results were further evaluated in vivo by performing uterotrophic assay in ovariectomized mouse models.
Results: At low concentration (40 μg/ml), SNGF induced a dose-dependent increase in MCF-7 cell proliferation, while higher extract concentrations (80-320 μg/ml) caused progressive cell growth inhibition. The competitive binding assay using [3] H-E 2 suggests that this effect is mediated by estrogen receptor. Mouse uterotrophic assay revealed a classical uterotrophic response in ovariectomized mice in response to S. nigrum glycoside fraction (SNGF). SNGF at a dose of 100 mg/kg of body wt induced the maximum height of luminal epithelial cells which indicated an increase of 30.8 per cent over control (P<0.01) with a correlated increase in uterine wet wt (150% increase over control). Higher doses (250 and 500 mg/kg body wt) of SNGF did not induce any uterotrophic effect.
Interpretation & conclusions : Our preliminary data demonstrate the hormone like activity of Solanum glycosides both in vitro and in vivo in mouse, which needs to be further explored to evaluate the possible mechanism and clinical implications.

Keywords: Estrogen receptor - glycosides - Solanum nigrum - solasodine - uterotrophic assay


How to cite this article:
Jisha S, Sreeja S, Manjula S. In vitro & in vivo estrogenic activity of glycoside fractions of Solanum nigrum fruit. Indian J Med Res 2011;134:369-74

How to cite this URL:
Jisha S, Sreeja S, Manjula S. In vitro & in vivo estrogenic activity of glycoside fractions of Solanum nigrum fruit. Indian J Med Res [serial online] 2011 [cited 2020 Feb 23];134:369-74. Available from: http://www.ijmr.org.in/text.asp?2011/134/3/369/85577

Solanum nigrum (Black night shade) is used as fruit and leafy vegetable in Southeast Asia, the Americas and several places in Africa. The plant reportedly provides appreciable amounts of minerals including calcium, iron and phosphorous, vitamins A and C, as well as proteins and amino acid methionine, scarce in other commonly marketed vegetables [1] . The plant extract is widely used in traditional systems of medicine for its diuretic, anti- pyretic and anti-inflammatory properties [2] and has a spasmolytic action on the uterus [3] . In certain tribes, fruits of S. nigrum are used as an oral contraceptive, and the plant is one of the main constituents of plant based remedy prescribed for dysfunctional uterine bleeding [3] . The medicinal effects of the plant are attributed to the presence of solasodine, a steroidal glycoalkaloid, which is a potential alternative to diosgenin for commercial synthesis of various steroidal drugs [4] . Solasodine in the plant is bound to a series of sugar residues attached to the oxygen atom at C-3; most common forms are the triglycosides and solamargine [5] . The biological effect of mixture of Solanum glycosides is restricted to studies on certain basal cell carcinomas [6],[7] . There is one report of the presence of estrogen receptor (ER)-like proteins and endogenous ligands for ER in S. glaucophyllum[8] . The present study was primarily aimed at assessing the estrogenic potential of the fruits of this edible and medicinal Solanum species- S. nigrum, in vitro in MCF-7 cell lines and in vivo in animal model.


   Material and Methods Top


Plant material: Authentic certified seeds of S. nigrum (Acc No. IC 298650) procured from National Bureau of Plant Genetic Resources (NBPGR), Kerala Agricultural University Campus, Thrissur, Kerala, were planted and maintained in the green house of Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, Kerala, under uniform conditions of temperature and humidity.

Phytochemical extraction: Mature, unripe fruits from two months old plants were collected, washed and oven dried at 60° C. Uniformly dried fruits were powdered and 100 g of dried powder was used for soxhlet analysis. Extraction was carried out sequentially with 250 ml hexane and 250 ml chloroform at 50° C for 18 h to remove the less polar lipid components and finally with 250 ml methanol at a temperature of 50° C for 18 h to obtain the glycoside fraction. The defatted methanol fraction was further purified in silica gel glass column (Borosil) using the solvent mixture of 66 methanol: 33 chloroform: 1 glacial acetic acid as the mobile phase. The fractions were separately analyzed for the presence of glycosides by thin layer chromatography (TLC) performed on pre-coated TLC plates (Silica gel 60 TLC Plates, Merck, Germany). The solasodine glycoside, α - solanine was used as standard and the spots were visualized under UV light. Fractions from seven to fifteen which showed spots corresponding to the standard were pooled and dissolved in methanol followed by centrifugation at 7500 g for 5 min and the supernatant was collected. This was air-dried to remove traces of methanol and finally dissolved in distilled water at required concentrations to serve as the Solanum nigrum glycoside fraction (SNGF) used for further studies.

Cell viability assay: MCF-7 cell lines (Acc No. HTB-22) procured from ATCC (Rockville, MD, USA) were revived in Dulbecco's minimum essential medium (DMEM) phenol red free medium (Sigma, USA) containing 20 per cent foetal bovine serum (FBS) from Invitrogen (USA) and cultured in DMEM containing 10 per cent FBS. Cells were maintained in an incubator at 37° C under 5 per cent CO 2 . After attaining confluence, the cells were trypsinized in 0.25 per cent (w/v) trypsin to detach from the flask and the suspended cells were centrifuged at 3500 rpm for 5 min in a centrifuge. Pellets were re-suspended in 7 ml DMEM medium and 100 μl each was poured into each well of a 96 well ELISA plate (BD Falcon, USA). Cells were incubated for a period of 48 h. The stock containing the glycoside fraction was prepared in 100 mg/ml of DMSO [methyl sulfinyl methane, Sisco Research Laboratory (India)]. Five dilutions of the extract were prepared in serum free medium which include 1:500 (320 μg of SNGF), 1:1000 (160 μg of SNGF), 1:2000 (80 μg of SNGF), 1:4000 (40 μg of SNGF) and 1: 8000 (20 μg of SNGF). After allowing the cell lines to grow for a period of48 h, the medium was removed and 100 μl each of diluted SNGF was added in each cell. After 48 h, the medium was replaced by MTT reagent [3- (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide] dissolved in DMEM containing 2 per cent FBS and incubated at 37 0 C for 2 h; 100 μl of lysis buffer (pH 7.4 ) containing 5 mM Tris and 1 mM EDTA was added to each well and cultures were incubated for 4 h. The absorbance of the coloured solution was measured at 570 nm in a microplate reader (Bio-Rad, Model 680, USA).

Evaluation of estrogenic activity in vitro by hydroxy apatite (HAP) binding assay: HAP binding assay for estrogen receptor binding [9] was carried out for assessing the estrogenic potential of SNGF on MCF-7 cell line. Commercially available HAP (Sigma, USA) was used in this assay. Aliquots containing 15 μg of protein (MCF- 7 cytosol) were incubated overnight with varying concentrations of methanol extract and 20 nM final concentration of [3 H]- estradiol ( 3 H-E 2 ) ± 100 fold molar excess of diethylstilbestrol (DES) (Sigma, USA) at 4°C in a final volume of 200 μl. After overnight incubation, 250 μl of a 60 per cent HAP suspension in TEM buffer (pH 7.6) was added and the mixture was kept in ice for 15 min. After washing twice with ice cold TEM buffer, the HAP pellet, collected following centrifugation, was extracted with 1 ml ethanol. The radioactivity in the ethanol extract was measured. Non-specific binding was determined in the presence of a 100-fold excess DES and was subtracted from total binding.

Evaluation in vivo on animal models: Swiss albino mice from Sree Chitra Thirunal Institute of Medical Science and Technology (SCTIMST), Thiruvananthapuram, Kerala, were housed within temperature controlled (22 ± 2° C) conditions in the animal house facility of Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram. Mice were maintained on a 12 h light: 12 h darkness photoperiod and food and water were available ad libitum. Female mice (3 months old, 20-25 g) were ovariectomized and rested for ten days before receiving treatment. The treatment groups were administered orally for seven days with 200 μl each of SNGF alone at concentrations of 100, 250 and 500 mg/kg body wt/ day, distilled water alone (control group), or with 17β-estradiol (E2 ) alone (Sigma, USA) at a dose of 1 mg/kg body wt, which served as the positive control group. After seven days, mice were weighed and sacrificed by cervical dislocation and their uteri were dissected out, blotted and the wet wt recorded. All the protocols for animal experiments were approved by the Ethics Committee for Animal Experiment of Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram.

Histological analysis: The uteri were immediately fixed in 10 per cent formaldehyde. One horn of each uterus was dissected transversely and microtome sections of the tissues were stained by haematoxylin and eosin method [10] . The sections were used for morphometric determination of changes in luminal epithelium.

Morphometric analysis: The height of the luminal epithelium was determined using optical micrometer attached to the fluorescent microscope (Nikon Instruments Inc, NY, USA). Four measurements were made within four areas of each uterus.

Statistical analysis: All experiments were performed in 5 replicates and results are presented as mean ± SEM. Data were analyzed by one-way ANOVA. The differences between treatments were tested by Fisher's least significant difference test.


   Results and Discussion Top


SNGF treatment at 40 μg/ml resulted in proliferation of MCF-7 cells, whereas it inhibited MCF-7 cell proliferation at concentrations ranging from 80 to 320 μg/ml [Figure 1], which is 30 to 60 per cent lower than MCF-7 control. SNGF significantly inhibited the binding of [ 3 H]-E 2 to cytosolic estrogen receptor in a dose dependent manner. The IC 50 value of SNGF is 40 ± 5 μg/ml [Figure 2]. The results of competitive binding assay using [ 3 H]-E 2 suggest that stimulation of cell proliferation at low concentration is likely to be mediated via the estrogen receptor. This observation is in consonance with similar findings with soy isoflavone phytoestrogen, genistein [11],[12] . In a recent report, extracts of Chinese licorice (Glycyrrhiza uralensis) exhibited ER-dependent MCF-7cell proliferation at low concentrations and an anti-proliferative activity at higher concentrations which was found to be ER- independent [13] . Our observations in S. nigrum are in agreement with these reports but further studies are needed to conclude whether the anti-proliferative activity of SNGF at higher concentrations is ER-independent.
Figure 1: MTT assay shows proliferative effect of SNGF on MCF-7 cells at a concentration of 40 μg/ml concentration and an inhibition of cell proliferation at higher concentrations (80-320 μg/ml). The MCF-7 cells were treated with SNGF at concentrations ranging from 20-320 μg/ml. Values are means ± SE of 5 replicates.

Click here to view
Figure 2: HAP binding assay result shows that SNGF at a concentration of 40 μg/ml reduces the specific radioligand binding of the control (17 μ - E2) to the ER by 50 per cent.

Click here to view


The uteri from mice treated with 100 mg/kg of body wt appeared stouter and swollen, which upon sectioning, was found filled with fluid. Histological observations revealed that this lowest dose of SNGF induced the maximum height of luminal epithelial cells [Figure 3],[Figure 4]b which indicated an increase of 30.8 per cent over control (P<0.01), in addition to effecting stromal cell differentiation and glandular proliferation [Figure 4]c, which were not observed in uterus from control mice. Treatment with E 2 induced an increase of luminal epithelial cell height of 84.6 per cent ([Figure 3]; P<0.001) over control [Figure 4]a. Higher concentrations did not affect a significant increase in cell height relative to control. The SNGF when fed to the ovariectomized mice at a concentration of 100 mg/kg body wt also significantly increased the wet wt of the uterus relative to the control group (P<0.001). There was a 150 per cent increase in uterine wet wt in response to100 mg/kg concentration of extract and a 283 per cent increase in response to positive E 2 (P<0.001). Wet wt of the uterus calculated as a percentage of the body wt showed a similar change in pattern in response to treatment. Higher concentrations (250 and 500 mg/kg of body wt/day) of SNGF did not produce a significant increase in uterine wet wt compared to control [Figure 5].
Figure 3: Effect of SNGF on ovariectomized mouse uterine epithelial cells. Water fed ovariectomized mice served as control; treatment group mice were fed with 100, 250 & 500 mg/kg body wt of SNGF. They were sacrificed after 7 days of treatment and the uteri were collected. Result indicated an increase in uterine cell height of animals treated with 100 mg/kg SNGF which is 30.8 per cent more than the control. Values represent the mean ± SE values obtained from 5 animals per treatment. P **<0.01, P ***<0.001 compared to control.

Click here to view
Figure 4: Photomicrographs of Heamatoxylin and Eosin (H&E) stained sections of ovariectomized Swiss albino mice. (a) Water vehicle (control); (b & c) treatment with 100 mg/kg of body wt of SNGF; (b) arrow shows increase in luminal epithelial cell height compared to control; (c) increase in gland number in response to SNGF (10X magnification).

Click here to view
Figure 5: Effect of SNGF on uterine wet wt to body wt ratio of ovariectomized Swiss albino mice. The result shows a 150 per cent increase in uterine wet wt in response to 100 mg/kg concentration of SNGF and a 283 per cent increase in response to positive E2 (P<0.001). Higher concentrations (250, 500 mg/kg body wt/day) of SNGF did not produce a significant increase in uterine wet wt compared to control. Values are means ± SE of 5 replicates. P ***<0.001 compared to control.

Click here to view


The uterotrophic assay has been traditionally used to establish the estrogenic effects of suspected estrogens and is still used as a gold standard for in vivo assessment of estrogenic activity. The uterus responds to cyclical changes in estrogen and progesterone levels in preparation for embryo implantation and estrogen mediates the principal proliferative response of the uterus through the estrogen receptors [14],[15] . In uterus, the physiological and genomic responses to estrogen have been described as biphasic. The events include hyperemia and uterine fluid uptake or water imbibition [16] . The water imbibition results in rapid increase in uterine wet wt. The late phase response to estrogen includes epithelial cell proliferation and differentiation [17] . SNGF at low concentrations displays uterotrophic activity that is not observed at higher concentrations which seems to depress the uterotrophic response to below the control levels. Similar observations from previous studies led to the conclusion that the uterotrophic and the estrogen agonistic effect presented by various natural estrogens occur at low doses only [18],[19],[20] . The results confirm the calabrese's concept of hormone-like biphasic dose response model which is characterized by a low-dose stimulation which usually present a modest response (30-60% vs. control) and a high-dose inhibition [21],[22],[23] as revealed in our studies on S. nigrum, indicating that a classical uterotrophic response occurs in the mouse uterus in response to SNGF.

In conclusion, our data showed hormone like activity of Solanum glycosides indicated by their ability to bind estrogen receptor in vitro. SNGF is less active than E 2 , but has potencies comparable to other known phytoestrogens. Further studies need to be done to understand the mechanism and clinical implications.


   Acknowledgment Top


This work was financially supported by Indian Council of Medical Research, New Delhi. Authors thank Dr Santhosh Kumar S, Veterinary surgeon, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, Kerala, for helping in the animal surgical procedures and Dr Mangalam S. Nair of Natural Products Synthesis, National Institute for Interdisciplinary Science and Technology, Government of India, for help provided in carrying out the phytochemical analyses.

 
   References Top

1.Padulosi S, Hoeschle-Zeledon I. Underutilized plant species: What are they? Leisa 2004; 20 : 5-6.  Back to cited text no. 1
    
2.Zakaria ZA, Gopalan HK, Zainal H, Mohd Pojan NH, Morsid NA, Aris A, et al. Antinociceptive, anti-inflammatory and antipyretic effects of Solanum nigrum chloroform extract in animal models. Yakugaku Zasshi 2006; 126 : 1171-8.  Back to cited text no. 2
    
3.Nevrekar P, Bai N, Khanna S. EveCare capsules in DUB. Obstet Gynaecol Commun 2002; 3 : 51-3.  Back to cited text no. 3
    
4.Galanes IT, Webb DT, Rosario OJ. Steroid production by callus and cell suspension cultures of Solanum aviculare.J Natl Prod 1984; 47 : 373-6.  Back to cited text no. 4
    
5.Bhat MA, Ahmad S, Aslam J, Mujib A, Mahmooduzzfar. Salinity stress enhances production of solasodine in Solanum nigrum L. Chem Pharmacol Bull 2008; 56 : 17-21.  Back to cited text no. 5
    
6.Cham BE. Solasodine glycosides as anti-cancer agents: preclinical and clinical studies. Asia Pac J Pharmacol1994; 9 : 113-8.  Back to cited text no. 6
    
7.Punjabi S, Cook LJ, Kersey D, Marks R, Cerio R. Solasodine glycoalkaloids: a novel topical therapy for basal cell carcinoma. A double- blind, randomized, placebo- controlled, parallel group, multicenter study. Int J Dermatol 2008; 47 : 78-82.   Back to cited text no. 7
    
8.Milanesi L, Boland R. Presence of estrogen receptor (ER)-like proteins and endogenous ligands for ER in Solanaceae. Plant Sci 2004; 166 : 397-404.  Back to cited text no. 8
    
9.Clark JH, Peck EJ Jr. Female sex steroids receptors and function. In: Gross F, Labhart A, Mann T, Bandes J, editors. Monographs on endocrinology. New York: Springer-Verlag; 1979. p. 28-36.   Back to cited text no. 9
    
10.Mayer P. Hematoxylin and eosin (H&E) staining protocol. Mitt Zool Stn Neapel 1896; 12 : 303.  Back to cited text no. 10
    
11.Wang TTY, Sathyamoorthy N, Phang JM. Molecular effects of genistein on estrogen receptor mediated pathways. Carcinogenesis 1996; 17 : 271-5.  Back to cited text no. 11
    
12.Hsieh CY, Santell RC, Haslam SZ, Helferich WG. Estrogenic effects of genistein on the growth of estrogen receptor-positive human breast cancer (MCF-7) cells in vitro and in vivo. Cancer Res 1998; 58 : 3833-8.  Back to cited text no. 12
    
13.Hu C, Liu H, Du J, Mo B, Qi H, Wang X, et al. Estrogenic activities of extracts of Chinese licorice (Glycyrrhiza uralensis) root in MCF-7 breast cancer cells. J Steroid Biochem Mol Biol 2009; 113 : 209-16.  Back to cited text no. 13
    
14.O'Brien JE, Peterson TJ, Tong MH, Lee EJ, Pfaff LE, Hewitt SC, et al. Estrogen-induced proliferation of uterine epithelial cells is independent of estrogen receptor á binding to classical estrogen response elements. J Biol Chem 2006; 281 : 26683-92.  Back to cited text no. 14
    
15.Katzenellenbogen BS, Bhakoo HS, Ferguson ER, Lan NC, Tatee T, Tsai TS, et al. Estrogen and antiestrogen action in reproductive tissues and tumors. Recent Prog Horm Res 1979; 35 : 259-300.  Back to cited text no. 15
    
16.Hewitt SC, Deroo BJ, Hansen K, Collins J, Grissom S, Afshari CA. Estrogen receptor-dependent genomic responses in the uterus mirror the biphasic physiological response to estrogen. Mol Endocrinol 2003; 17 : 2070-83.  Back to cited text no. 16
    
17.Couse JF, Korach KS. Estrogen receptor null mice: what have we learned and where will they lead us?. Endocrin Rev 1999; 20 : 358-417.  Back to cited text no. 17
    
18.Wanibuchi H, Kang JS, Salim EI, Morimura K, Fukushima S. Toxicity vs. beneficial effects of phytoestrogens. Pure Appl Chem 2003; 75 : 2047-53.  Back to cited text no. 18
    
19.Owens W, Ashby J, Odum J, Onyon L. The OECD program to validate the rat uterotrophic bioassay. Phase 2: dietary phytoestrogen analyses. Environ Health Perspect 2003; 111 : 1559-67.  Back to cited text no. 19
    
20.Yamasaki K, Takeyoshi M, Sawaki M, Imatanaka N, Shinoda K, Takatsuki M. Immature rat uterotrophic assay of 18 chemicals and Hershberger assay of 30 chemicals. Toxicology 2003; 183 : 93-115.  Back to cited text no. 20
    
21.Calabrese EJ, Baldwin LA. The hormetic dose-response model is more common than the threshold model in toxicology. Toxicol Sci 2003; 71 : 246-50.  Back to cited text no. 21
    
22.Chearskul S, Kooptiwut S, Chatchawalvanit S, Onreabroi S, Churintrapun M, Saralamp P, et al. Morinda citrifolia has very weak estrogenic activity in vivo. Thai J Physiol Sci 2004; 17 : 22-9.  Back to cited text no. 22
    
23.Frida L, Rakotonirina S, Rakotonirina A, Savineau JP. In vivo and in vitro effects of Bidens pilosa L. (Asteraceae) leaf aqueous and ethanol extracts on primed-oestrogenized rat uterine muscle. Afr J Tradit Complement Altern Med2007; 5 : 79-91.  Back to cited text no. 23
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]



 

Top
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
    Abstract
   Material and Methods
    Results and Disc...
   Acknowledgment
    References
    Article Figures

 Article Access Statistics
    Viewed877    
    Printed47    
    Emailed0    
    PDF Downloaded244    
    Comments [Add]    

Recommend this journal