Secondary Metabolites from Pepper (Piper Nigrum) and Tahitian Noni (Morinda Citrifolia) and Their Biological Activities
Wen, Yin Ping (2009) Secondary Metabolites from Pepper (Piper Nigrum) and Tahitian Noni (Morinda Citrifolia) and Their Biological Activities. Masters thesis, Universiti Putra Malaysia.
Piper nigrum from the Piperaceae family and Morinda citrifolia from the Rubiaceae family were researched in this study. Detailed phytochemical investigations on the roots of these plants afforded ten pure compounds, which consists mainly of alkaloids and anthraquinones, and an acid. The structures of these compounds were elucidated based on 1H NMR, 13C NMR, COSY, DEPT, 2D NMR (HSQC and HMBC), mass spectrometry (MS), and Infrared spectroscopy (FTIR) analysis. Meanwhile, mixtures of compounds were identified through GCMS (gas chromatography-mass spectrometry). From the roots of Piper nigrum, the alkaloids obtained are piperine, pellitorine and aristolactam AII. Besides that, the acid, 3,4-methylenedioxy benzoic acid was also present in the roots of this plant. Meanwhile, anthraquinones and their derivatives such as 1-hydroxy-2-methylanthraquinone, damnacanthal, nordamnacanthal, 2-formyl-1-hydroxyanthraquinone, 2-ethoxy-1-hydroxyanthraquinone and morindone-6-methylether were obtained from the roots of Morinda citrifolia. Among these anthraquinones, 2-ethoxy-1-hydroxyanthraquinone is a new anthraquinone, while morindone-6-methylether is reported for the first time from the plant. In the larvicidal test against the larvae of Aedes aegypti, the ethyl acetate extract of the roots of Piper nigrum showed good activity against the larvae. Pellitorine, on the other hand, gave a significant activity followed by piperine which only gave a moderate activity. The acid and aristolactam AII gave negative results which indicated that they are not biologically active towards the larvae of Aedes aegypti. For Morinda citrifolia, only the chloroform extract and the two anthraquinones, 1-hydroxy-2-methylanthraquinone and damnacanthal are strongly active. From the cytotoxic activity, where tests were conducted using the HL-60 (Acute Promyelocytic Leukaemia) and MCF7 cell lines (Human Breast Adenocarcinoma), the ethyl acetate extract of Piper nigrum gave weak activity with an IC50 value of more than 30 μg/ml against the HL-60 cell line. However, in the tests against the same cell line using piperine and pellitorine, IC50 value of 7.5 μg/ml and 1.5 μg/ml, respectively, were obtained indicating the individual compounds to be strongly cytotoxic. Aristolactam AII gave weak activity with an IC50 value of more than 30 μg/ml when tested on the MCF-7. Compared to the extract and alkaloids from Piper nigrum, the extracts and anthraquinones from Morinda citrifolia gave better results against both HL-60 and MCF7 cell lines. Three extracts amongst the five tested showed significant bioactivity against the HL-60 cell. These are the hexane extract, chloroform extract and petroleum ether extract, with IC50 values of 1.70 μg/ml, 9.3 μg/ml and 11.0 μg/ml, respectively. The methanol and acetone extracts showed moderate activities against the same cell line (HL-60). Damnacanthal, nordamnacanthal and 1-hydroxy-2-methylanthraquinone which were from the hexane and chloroform extracts gave IC50 values of 1.6 μg/mL, 4.4 μg/mL and 15.0 μg/mL, respectively, against the same cell line (HL-60). A comparison of the IC50 values of different extracts against the two cell lines indicated that these extracts did not give satisfying results against the MCF7 cell lines with only the chloroform and petroleum ether extracts giving a moderate activity. The antifungal and antibacterial activities of the extracts and some compounds from the two plants were also evaluated. Fungi such as Aspergilius ochraceaus and Sacchoromyces cerevisiae were used in the antifungal screening. Meanwhile, MRSA, Pseudomonas aeruginosa, Salmonella choleraesuis and Bacillus subtilis were the microbes used in the antibacterial screenings. None of the extracts or alkaloids from Piper nigrum showed any inhibition in both screening. As for Morinda citrifolia, only the chloroform and methanol extracts, and damnacanthal exhibited medium inhibition for Bacillus subtilis in the antibacterial screening. However, in the screening against Salmonella choleraesuis, only the chloroform extract and damnacanthal showed weak inhibition. Meanwhile, nordamnacanthal is the only sample tested that showed a very weak inhibition. In the antifungal screening, the two microbes were shown to be lightly susceptible to the chloroform extract and damnacanthal.
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