Antimalarial Biflavonoids from the Roots of Ochna Serrulata (Hochst.) Walp
Total Page：16
File Type：pdf, Size：1020Kb
International Research Journal of Pure & Applied Chemistry 16(4): 1-9, 2018; Article no.IRJPAC.42440 ISSN: 2231-3443, NLM ID: 101647669 Antimalarial Biflavonoids from the Roots of Ochna serrulata (Hochst.) Walp Monica M. Ndoile1* and Fanie R. Van Heerden2 1Department of Chemistry, College of Natural and Applied Sciences, University of Dar es Salaam, P.O.Box 35061, Dar es Salaam, Tanzania. 2School of Chemistry and Physics, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa. Authors’ contributions This work was carried out in collaboration between both authors. Author FRVH designed the study and mobilized the resources. Author MMN engaged in laboratory activities and wrote the first draft of the manuscript. Data analyses, reading and approving the manuscript were done by both authors. Article Information DOI: 10.9734/IRJPAC/2018/42440 Editor(s): (1) Dr. Richard Sawadogo, Group Cell death & Natural Compounds, Laboratoire de Biologie Moléculaire et -Cellulaire du Cancer Hôpital Kirchberg, Luxembourg. Reviewers: (1) S. Murugesan, Pachaiyappa’s College, India. (2) Busari Musa Bola, Federal University of Technology Minna, Nigeria. Complete Peer review History: http://www.sciencedomain.org/review-history/25281 Received 9th April 2018 th Original Research Article Accepted 18 June 2018 Published 27th June 2018 ABSTRACT Aims: To isolate and evaluate the biological activities of the compounds present in the roots of Ochna serrulata. Study Design: Laboratory isolation of compounds by using various chromatographic methods, and cytotoxicity and antimalarial evaluations of the isolated compounds. Place and Duration of Study: School of Chemistry and Physics, College of Agriculture, Engineering and Science, University of KwaZulu-Natal (UKZN), from September 2009 to June 2012. Methodology: Methanol extract of the pulverised roots of O. serrulata were subjected to different chromatographic techniques. Structures were established by using 1D and 2D NMR techniques and MS. The compounds were subjected to cytotoxicity tests to evaluate their growth inhibitory effects on renal (TK 10), melanoma (UACC62) and breast (MCF7) cancer cell lines using a sulforhodamine B (SRB) assay. Antimalarial evaluations were done against chloroquine-resistant strains of Plasmodium falciparum (FCR-3). _____________________________________________________________________________________________________ *Corresponding author: E-mail: [email protected]; Ndoile and Heerden; IRJPAC, 16(4): 1-9, 2018; Article no.IRJPAC.42440 Results: Three new biflavonoids; 4,4′,7-tri-O-methylisocampylospermone A (1), 4‴-de-O- methylafzelone A (2) and serrulone A (3) along with irisolone 4′-methyl ether (4), 3',4'-dimethoxy- 6,7-methylenedioxyisoflavone (5), iriskumaonin 3′-methyl ether (6), lophirone L (7), a mixture of biflavanone 1 and campylospermone A, syringaresinol (8), and 16α,17-dihydroxy-ent-kauran-19-oic acid (9). Compound 1 showed antimalarial activity with IC50 11.46 µM, followed by compound 3 (26.52 µM) and lastly compound 2 (38.43 µM). In the same test, 4 demonstrated antimalarial activity at IC50 40.72 µM, 8 (42.66 µM), 6 (93.69 µM), 9 (106.48 µM) and the rest did not show any significant activity. Upon cytotoxicity evaluation against three different cancer cell lines, the compounds displayed no significant activity. Conclusion: The genus is comprised of biflavonoids of varying nature, some of which expressed interesting biological activities with no/low toxicity. Keywords: Biflavonoid; cytotoxicity; antimalarial; Ochna serrulata. 1. INTRODUCTION 2. MATERIALS AND METHODS The emergence of drug-resistant pathogens has 2.1 General Experimental Procedures devastated efforts of scientists in overcoming the burden of the diseases. The widespread and use Chromatotron (model 7924, Harrison Research), of substandard medicines have fuelled the centrifugal chromatography was used for emergence of drug-resistant pathogens. Simply, purification of the fractions, on a circular plate drug resistance can be viewed as a persistence that were coated with 2 or 4 mm thickness of a parasite even after proper treatment doses preparative silica gel. Silica gel 60F254, (40-63 have been taken [1,2]. So far, drug resistance μm, Merck) was used for column has become an obstacle towards disease chromatography. Acquisition of the 1H, COSY, eradication, thus creating an increasing gap for HSQC and HMBC NMR spectra recording at 500 new medicines. Nature has been known to have MHz/400 MHz and 125 MHz/100 MHz for 13C made a significant contribution in drug discovery was achieved by using Bruker Avance III 500 or and pharmacology, in the fight against diseases, Bruker Avance III 400 spectrometers. thus, provide a wealth of compounds as drug Referencing of chemical shifts was achieved by leads or novel structures. The use of plants for using residual solvent peaks. that is; chloroform: the medicinal purpose can be traced back since 1H 7.26 ppm, 13C, 77.0 ppm, methanol-d4: 1H man begun existing, thus a need to tap into this 3.31 ppm, 13C, 49.1 ppm, acetone-d6 1H 2.05 rich source of novel structures and new drugs. ppm, 13C, 29.9 ppm. The LCT Premier mass Locally, O. serrulata is called Umbomvane, spectrometer was used in Mass Spectrometry. fynblaarrooihout and iliTye in Zulu, Afrikaan and Data recording was taken on the time-of-flight Xhosa respectively. The plant belongs to genus (TOF) Waters using electrospray ionisation. ADP Ochna that has been deployed in various 440+ model polarimeter (Bellingham and Stanley traditional medicine systems for treatment of product) was used for optical rotations various ailments. In Zulu traditional medicine, the determinations. For separations monitoring, Thin- root decoction of the plant is commonly used for Layer Chromatographic plates (TLC; Kieselgel bone disease treatment and gangrenus proctitis 60 F254, 0.25mm) sprayed with anisaldehyde [3,4]. reagent followed by heating. Anisaldehyde stain solution was prepared following: ice cooling of Although there are many reports on the 465 mL methanol in a 1 L volumetric flask, on structures of the secondary metabolites from the stirring, an addition of 5 mL acetic acid followed leaves and stems of the genus, not many reports by 17 mL concentrated sulfuric acid and 13 mL of on structures of compounds from the roots of p-anisaldehyde. Ochna species. Nonetheless, to the best of our knowledge, phytochemical studies on the roots of 2.2 Plant Materials O. serrulata has never been done before, thus, this paper intends to report for the first time the The plant was collected from the botanical results of the phytochemical studies and garden of the University of KwaZulu-Natal biological activities of the compounds from the (UKZN) and identified by Allison Young from the roots of O. serrulata. botanical garden in September 2009. At the 2 Ndoile and Heerden; IRJPAC, 16(4): 1-9, 2018; Article no.IRJPAC.42440 herbarium of UKZN, voucher specimen 3. RESULTS AND DISCUSSION (reference number NU, M. Ndoile 01) was deposited. 3.1 Characterisation of the Compounds Isolated 2.2.1 Extraction and isolation Three new biflavonoids, namely, 4,4′,7-tri-O- Roots of O. serrulata (air-dried and ground; 1.2 methylisocampylospermone A (1), 4‴-de-O- kg) were soaked in MeOH at room temperature methylafzelone A (2) and serrulone A (3) were for 48 h to yield 15 g of the extract. Initial isolated, along with 4′-methoxyirisolone (4), 3′,4′- fractionation in a short silica gel column with dimethoxy-6,7-methylenedioxyisoflavone (5), 3′- mixtures of EtOAc-hexanes eluents (increasing methoxyiriskumaonin (6), lophirone L (7), polarity) to give five fractions (R.1-R.5), with the syringaresinol (8), 16α,17-dihydroxy-ent-kauran- fifth being MeOH wash. Upon dissolving fraction 19-oic acid (9), lophirone A, lophirone C, R.2 (850 mg) in MeOH, compound 9 precipitated afzelone B, 5-deoxyurundeuvine C and a mixture out as an off-white powder, thus washed further of biflavanone 1 and campylospermone A. The with MeOH to afford 15 mg. The remaining isolation of a furofuran lignan 8 (a major filtrate was subjected to repeated chromatotron constituent of genus syringa) [7] from the family with a DCM-hexanes mixture (1:1) to obtain a ochnaceae is hereby reported for the first time. A pale yellow amorphous solid of 4,4′,7-tri-O- diterpene of ent-kauranoic acid type [16α,17- methylisocampylospermone A (1) (14.2 mg), dihydroxy-ent-kauran-19-oic acid] was reported isoflavonoids 4 (9.1 mg), 5 (10.0 mg) and 6 (11.2 from Helianthus and Annona species [8,9], mg). however, its isolation from the family ochnaceae is reported herein for the first time. Fraction R.3 was subjected to repeated purification on a chromatotron with DCM:EtOAc The structures of all secondary metabolites were (1:1) eluent to afford lophirone A (8.1 mg), established by NMR spectroscopic and mass lophirone C (7.7 mg), afzelone B (10.1 mg) and spectrometric analyses, however, the observed 5-deoxyurundeuvine C (18.0 mg). and literature reported spectroscopic data were compared for further confirmation of the structures of the known compounds. Fraction R.4 (2.5 g) was fractionated in a silica gel column (DCM-EtOAc (1:1) eluent) to obtain four fractions (R4.1-R4.4). Fraction R4.1 (400 mg) and R4.2 (500 mg) were combined and the resulting mixture was purified repeatedly on a chromatotron with DCM-EtOAc (1:1) as a mobile phase to yield a yellow powder of compound 2 (19.0 mg), yellow solids of compound 3 (27.5 mg) and compound 8 (15 mg). R4.3 was combined with R4.4 and repeatedly purified on a chromatotron with EtOAc:DCM (6:4) eluent to afford 3 (5.1 mg) and yellow solids of 7 (7.2 mg). 2.3 Biological Assays 2.3.1 Cytotoxicity Compound 1 is a yellow non-crystalline solid with a molecular formula C33H28O8 confirmed by Growth inhibitory activity of all the isolated molecular ion peak [M-H]- at m/z = 551 in mass compounds was evaluated using renal (TK10), spectrometry.