BIOAUTOGRAPHY, COMBINATION EFFECTS AND PHOTO-ACTIVATED ENZYMATIC RESTRICTION INHIBITORY ACTIVITY OF ANTIMICROBIAL ALKALOIDS FROM GLYCOSMIS PENTAPHYLLA (RETZ.) DC.
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Published:
Oct 31, 2022
Keywords:
Alkaloids, antimicrobial, bioautography, Glycosmis pentaphylla, photo-activated DNA binding.
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Abstract
Glycosmis pentaphylla (Retz.) DC., locally known as nerapan, has long been used in Asian countries as a traditional remedy for ailments attributed to microbial infections. This study aims to isolate antimicrobial alkaloids from G. pentaphylla, to determine their combination effects with selected antimicrobial agents and to screen for their photoactivated enzymatic restriction inhibitory activity. Bioautography-guided isolation of antimicrobial alkaloids was performed by using column chromatography with Staphylococcus aureus, Escherichia coli, and Candida albicans as the indicator microbes. The antimicrobial effects of the alkaloids combined with selected antimicrobial agents, namely, ciprofloxacin, erythromycin, vancomycin, and ketoconazole, were determined by using a checkerboard assay. Photoactivated enzymatic restriction inhibitory activity was assessed by using agarose gel electrophoresis. Two antimicrobial active alkaloids were isolated and identified as arborinine and arborine. The antimicrobial activity of arborinine and arborine was determined to be in the range of 250 µg/ml and 1000 µg/ml. Partial synergy was observed for all arborine-antibiotics and arborinine-ketoconazole interactions against S. aureus and C. albicans, respectively. Arborine was relatively the strongest photoactivated enzymatic restriction inhibitor, particularly against EcoRI, PstI, and SalI. The results obtained are promising and encourage further research on alkaloids as potential antimicrobial-enhancing agents.
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Md Taib, N., Hassan, N. M., Mohd Kamal, L. Z., & Khin Soe, M. (2022). BIOAUTOGRAPHY, COMBINATION EFFECTS AND PHOTO-ACTIVATED ENZYMATIC RESTRICTION INHIBITORY ACTIVITY OF ANTIMICROBIAL ALKALOIDS FROM GLYCOSMIS PENTAPHYLLA (RETZ.) DC. Malaysian Journal of Science, 41(3), 1–9. https://doi.org/10.22452/mjs.vol41no3.1
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References
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Asif, M. (2014). Chemical characteristics, synthetic methods, and biological potential of quinazoline and quinazolinone derivatives. International Journal of Medicinal Chemistry 395637. doi: 10.1155/2014/395637
Aye, M. M., Aung, H. T., Sein, M. M. & Armijos, C. (2019). A Review on the phytochemistry, medicinal properties and pharmacological activities of 15 selected Myanmar medicinal plants. Molecules 24: 293. doi:10.3390/molecules24020293
Battacharyya, P., Cakrabartty, P. K. & Chowdury, B. K. (1985). Glycozolidol, an antibacterial carbazole alkaloid from Glycosmis pentaphylla. Phytochemistry 24(4): 882-883.
Bhardwaj, M., Singh, B. R., Sinha, D. K., Kumar, V., Prasanna Vadhana, O. R., Varan Singh, S., Nirupama, K. R., Pruthvishree, Archana Saraf, B. S. (2016). Potential of herbal drug and antibiotic combination therapy: A new approach to treat multidrug resistant bacteria. Pharmaceutica Analytica Acta 7(11): 1-14. doi: 10.4172/2153-2435.1000523
Bollenbach, T. (2015). Antimicrobial interactions: mechanisms and implications for drug discovery and resistance evolution. Current Opinion in Microbiology 27: 1-9. doi: 10.1016/j.mib.2015.05.008.
Bulbul, I. J. & Jahan, N. (2016). Study on antioxidant and antimicrobial activities of methanolic leaf extract of Glycosmis pentaphylla against various microbial strains. Journal of Pharmacognosy and Phytochemistry 5(4): 53-57.
Cheesman, M. J., Ilanko, A., Blonk, B. & Cock, I. E. (2017). Developing new antimicrobial therapies: Are synergistic combinations of plant extracts/compounds with conventional antibiotics the solution? Pharmacognosy Review 11: 57-72.
Chen, Y., Tang, C., Wu, Y., Mo, S., Wang, S., Yang, G. & Mei, Z. (2015). Glycosmisines A and B: isolation of two new carbazole–indole-type dimeric alkaloids from Glycosmis pentaphylla and an evaluation of their antiproliferative activities. Organic & Biomolecular Chemistry 13(24): 6773-6781.
Choi, J. G., Kang, O. H., Lee, Y. S., Oh, Y. C., Chae, H. S., Jang, H. J., Shin, D. W. & Kwon, D. Y. (2009). Antibacterial activity of methyl gallate isolated from Galla rhois or carvacrol combined with nalidixic acid against nalidixic acid resistant bacteria. Molecules 14(5): 1773-1780. doi: 10.3390/molecules14051773
Chua, L. S. L. & van Valkenberg, J. L. C. H. (2001). Glycosmis pentaphylla (Retz.) A.D.C. In: van Valkenberg,, J. L. C. H. & Bunyapraphatsara, N. (editors). Plant Resources of South East Asia 12(2): Medicinal and Poisonous Plants 2, pp. 275-278, Leiden: Backhuys Publishers.
CLSI (2006). Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically, Approved Standard Seventh Edition, Document M7-A7 [ISBN 1-56238-587-9]. Wayne: Clinical and Laboratory Standards Institute.
Cui, J., Ren, B., Tong, Y., Dai, H. & Zhang, L. (2015). Synergistic combinations of antifungals and anti-virulence agents to fight against Candida albicans. Virulence 6(4): 362-371.
Das, M. M. & Deka, D. C. (2017). Evaluation of anticancer and antimicrobial activity of arborinine from Glycosmis pentaphylla. Journal of Biologically Active Products from Nature 7(2): 131-139.
da Silva, M. F. G. F., Fernandes, J. B., Forim, M. R., Vieira, P. C. & de Sa´, I. C. G. (2013). Alkaloids derived from anthranilic acid: Quinoline, acridone and quinazoline. In: K. G. Ramawat, and J. M. Me´rillon (eds.). K. G. Ramawat, and J. M. Me´rillon (eds.). Natural Products, pp. 715-859, Berlin Heidelberg: Springer-Verlag.
Dewanjee, S., Gangopadhyay, M., Bhattacharya, N., Khanra, R. & Dua, T. K. (2015). Bioautography and its scope in the field of natural product chemistry. Journal of Pharmacceutical Analysis 5(2): 75–84.
Farediah, A., Hazar Bebe, M. I. & Mawardi, R. (1996). Arborine, a larval growth inhibitor from Glycosmis pentaphylla. Pertanika Journal of Science and Technology 4(1): 11-15.
Fothergill, A.W. (2014). Miconazole: a historical perspective. Expert Review of Anti-infective Therapy 4(2): 171-175.
Hanawa, F., Fokialakis, N. & Skaltsounis, A-L. (2004). Photo activated DNA binding and antimocrobial activities of furoquinoline and pyranoquinolone alkaloids from Rutaceae. Planta Medica 70: 531-535.
Hanawa, F., Okamoto, M. & Towers, G. H. N. (2001). Inhibition of restriction enzyme’s DNA sequence recognition by PUVA treatment. Photochemistry Photobiology 74(2): 269-273.
Hassan, S. A., Barthwal, R., Padmadeo, S. R. & Barukab, O. M. (2014). Restriction inhibition assay: A qualitative and quantitative method to screen sequence specific DNA binder from herbal plants. Tropical Journal of Pharmaceutical Research 13(2): 267-273.
Hazarika, P. & Dutta, D. (2013). Traditional knowledge for using plant resources as tooth brushing stick (datun) by the indigenous communities of Assam, India. International Journal of Herbal Medicinal 6(6): 22-34.
He, D., Wang, M., Zhao, S., Shu, Y., Zeng, H., Xiao, C., Lu, C. & Liu, Y. (2017). Pharmaceutical prospects of naturally occurring quinazolinone and its derivatives. Fitoterapia 119:136-149.
Howlader, M. A., Farhana, R., Shapna, S., Mohammad, R. R., Shams-Ud-Doha, K.M., Rumana, M. & Apurba, S. A. (2011). Antimicrobial, antioxidant, and cytotoxic effects of methanolic extracts of leaves and stems of Glycosmis pentaphylla (Retz.). Journal of Applied Pharmaceutical Science 1(8):137-140.
Kamel, M. M., Zaghary, W. A., Al-Wabli, R. I. & Anwar, M. M. (2016). Synthetic approaches and potential bioactivity of different functionalized quinazoline and quinazolinone scaffolds. Egyptian Pharmaceutical Journal 15(3): 98-131.
Khameneh, B., Iranshahy, M., Soheili, V. & Bazzaz, B. S. F. (2019). Review on plant antimicrobials: a mechanistic viewpoint. Antimicrobial Resistence and Infection Control 8: 118. doi: 10.1186/s13756-019-0559-6
Kumar, A., Banerjee, N., Singamaneni, V., Dokuparthi, S. K., Chakrabarti, T. & Mukhopadhyay, S. (2018). Phytochemical investigations and evaluation of antimutagenic activity of the alcoholic extract of Glycosmis pentaphylla and Tabernaemontana coronaria. Natural Products Research 32(5), 582-587.
Leite, G. C., Neto, L. V. P., Gaudereto, J. J., de Maio Carrilho, C. M. D., Ross, F., Anna Sara Levin A. S. & Costa, S. F. (2015). Effect of antibiotics combination and comparison of methods of synergism in multiresistant Gram negative bacteria. Journal of Infectious Diseases and Therapy 3: 207. doi: 10.4172/2332-0877.1000207
Li, D-D., Xu, Y., Zhang, D-Z., Quan, H., Mylonakis, E., Hu, D-D., Li, M-B., Zhao, L-Z., Zhu, L-H., Wang, Y. & Jiang, Y. Y. (2013). Fluconazole assists berberine to kill fluconazole-fesistant Candida albicans. Antimicrobial Agents and Chemotherapy 57(12): 6016-6027.
Mat Salleh, K. & Latiff A. (2002). Tumbuhan Ubatan Malaysia. pp. 473, Bangi: Pusat Pengurusan Penyelidikan Universiti Kebangsaan Malaysia.
Mawardi, R., Rosmiati, M. S., Najihah, M. H., Mohd Aspollah, S., Gwendoline, C. L. E., Abdul Manaf, A. & Hazar Bebe, M. I. (2010). Alkaloids and sulphur-containing amides from Glycosmis citrifolia and Glycosmis elongata. Sains Malaysiana 39(3): 445-451.
Mohamed, M. A., Ghanem, H. M., Abd El-Ghaffar, N. F. & Mohamed, S. S. (2013). Biological evaluation and molecular docking of substituted quinazolinones as antimicrobial agents. Australian Journal of Basic and Applied Sciences 7: 263–274.
Mohd Kamal, L. Z., Mohd Hassan, N., Md Taib, N. & Soe, M. K. (2018). Graveoline from Ruta angustifolia (L.) Pers. and its antimicrobial. synergistic potential in erythromycin or vancomycin combinations. Sains Malaysiana 47(10): 2429-2435.
Monte, J., Abreu, A. C., Borges, A., Simões, L. C. & Simões, M. (2014). Antimicrobial activity of selected phytochemicals against Escherichia coli and Staphylococcus aureus and their biofilms. Pathogens 3(2): 473-498. doi:10.3390/pathogens3020473
Murugan, N. & Natarajan, D. (2016). Phytochemical, antioxidant and antibacterial activities of Glycosmis pentaphylla (Rutaceae) leaf extracts against selected multi-drug resistant bacteria. Journal of Chemical and Pharmaceutical Research 8(1): 737-744.
Rahalison, L., Hamburger, M., Hostettmann, K., Monod, M. & Frenk, E. (1991). Bioautographic agar overlay method for the detection of antifungal compounds from higher plants. Phytochemical Analysis 2:199-203.
Sreejith, P. S., Praseeja, R. J. & Asha, V. V. (2012). A review on the pharmacology and phytochemistry of traditional medicinal plant, Glycosmis pentaphylla (Retz.) Correa. Journal of Pharmacy Research 5(5): 2723-2728.
Tillequin F. (2007). Rutaceous alkaloids as models for the design of novel antitumor drugs. Phytochemistry Review 6: 65-79.
van Vuuren, S. & Viljoen, A. (2011). Plant-based antimicrobial studies - Methods and approaches to study the interactions between natural products. Planta Medica 77: 1168-1182.
Wang, J., Di, Y., Yang, X., Li, S., Wang, Y. & Hao, X. (2006). Hydroquinone diglycoside acyl esters from the stems of Glycosmis pentaphylla. Phytochemistry 67(5): 486-491.
Yang, G.-Z., Wu, Y. & Chen, Y. (2012). Alkaloids from the stems of Glycosmis pentaphylla. Helvetica Chimica Acta 95: 1449–1451.
Yu., C., Bo, Y., Jing, X., Tong, Z., Hua, F. & Guang-zhong, Y. (2012). Photo-activated DNA binding and antimicrobial activities of alkaloids from Glycosmis pentaphylla. Acta Pharmaceutica Sinica 47(12): 1646−1652.
Zhou, A., Kang, T. M., Yuan, J., Beppler, C., Nguyen, C., Mao, Z., Nguyen, M. Q., Yeh, P. & Miller, J. H. (2015). Synergistic interactions of vancomycin with different antibiotics against Escherichia coli: Trimethoprim and nitrofurantoin display strong synergies with vancomycin against wild-type E. coli. Antimicrobial Agents and Chemotherapy 59(1): 276-281.
Asif, M. (2014). Chemical characteristics, synthetic methods, and biological potential of quinazoline and quinazolinone derivatives. International Journal of Medicinal Chemistry 395637. doi: 10.1155/2014/395637
Aye, M. M., Aung, H. T., Sein, M. M. & Armijos, C. (2019). A Review on the phytochemistry, medicinal properties and pharmacological activities of 15 selected Myanmar medicinal plants. Molecules 24: 293. doi:10.3390/molecules24020293
Battacharyya, P., Cakrabartty, P. K. & Chowdury, B. K. (1985). Glycozolidol, an antibacterial carbazole alkaloid from Glycosmis pentaphylla. Phytochemistry 24(4): 882-883.
Bhardwaj, M., Singh, B. R., Sinha, D. K., Kumar, V., Prasanna Vadhana, O. R., Varan Singh, S., Nirupama, K. R., Pruthvishree, Archana Saraf, B. S. (2016). Potential of herbal drug and antibiotic combination therapy: A new approach to treat multidrug resistant bacteria. Pharmaceutica Analytica Acta 7(11): 1-14. doi: 10.4172/2153-2435.1000523
Bollenbach, T. (2015). Antimicrobial interactions: mechanisms and implications for drug discovery and resistance evolution. Current Opinion in Microbiology 27: 1-9. doi: 10.1016/j.mib.2015.05.008.
Bulbul, I. J. & Jahan, N. (2016). Study on antioxidant and antimicrobial activities of methanolic leaf extract of Glycosmis pentaphylla against various microbial strains. Journal of Pharmacognosy and Phytochemistry 5(4): 53-57.
Cheesman, M. J., Ilanko, A., Blonk, B. & Cock, I. E. (2017). Developing new antimicrobial therapies: Are synergistic combinations of plant extracts/compounds with conventional antibiotics the solution? Pharmacognosy Review 11: 57-72.
Chen, Y., Tang, C., Wu, Y., Mo, S., Wang, S., Yang, G. & Mei, Z. (2015). Glycosmisines A and B: isolation of two new carbazole–indole-type dimeric alkaloids from Glycosmis pentaphylla and an evaluation of their antiproliferative activities. Organic & Biomolecular Chemistry 13(24): 6773-6781.
Choi, J. G., Kang, O. H., Lee, Y. S., Oh, Y. C., Chae, H. S., Jang, H. J., Shin, D. W. & Kwon, D. Y. (2009). Antibacterial activity of methyl gallate isolated from Galla rhois or carvacrol combined with nalidixic acid against nalidixic acid resistant bacteria. Molecules 14(5): 1773-1780. doi: 10.3390/molecules14051773
Chua, L. S. L. & van Valkenberg, J. L. C. H. (2001). Glycosmis pentaphylla (Retz.) A.D.C. In: van Valkenberg,, J. L. C. H. & Bunyapraphatsara, N. (editors). Plant Resources of South East Asia 12(2): Medicinal and Poisonous Plants 2, pp. 275-278, Leiden: Backhuys Publishers.
CLSI (2006). Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically, Approved Standard Seventh Edition, Document M7-A7 [ISBN 1-56238-587-9]. Wayne: Clinical and Laboratory Standards Institute.
Cui, J., Ren, B., Tong, Y., Dai, H. & Zhang, L. (2015). Synergistic combinations of antifungals and anti-virulence agents to fight against Candida albicans. Virulence 6(4): 362-371.
Das, M. M. & Deka, D. C. (2017). Evaluation of anticancer and antimicrobial activity of arborinine from Glycosmis pentaphylla. Journal of Biologically Active Products from Nature 7(2): 131-139.
da Silva, M. F. G. F., Fernandes, J. B., Forim, M. R., Vieira, P. C. & de Sa´, I. C. G. (2013). Alkaloids derived from anthranilic acid: Quinoline, acridone and quinazoline. In: K. G. Ramawat, and J. M. Me´rillon (eds.). K. G. Ramawat, and J. M. Me´rillon (eds.). Natural Products, pp. 715-859, Berlin Heidelberg: Springer-Verlag.
Dewanjee, S., Gangopadhyay, M., Bhattacharya, N., Khanra, R. & Dua, T. K. (2015). Bioautography and its scope in the field of natural product chemistry. Journal of Pharmacceutical Analysis 5(2): 75–84.
Farediah, A., Hazar Bebe, M. I. & Mawardi, R. (1996). Arborine, a larval growth inhibitor from Glycosmis pentaphylla. Pertanika Journal of Science and Technology 4(1): 11-15.
Fothergill, A.W. (2014). Miconazole: a historical perspective. Expert Review of Anti-infective Therapy 4(2): 171-175.
Hanawa, F., Fokialakis, N. & Skaltsounis, A-L. (2004). Photo activated DNA binding and antimocrobial activities of furoquinoline and pyranoquinolone alkaloids from Rutaceae. Planta Medica 70: 531-535.
Hanawa, F., Okamoto, M. & Towers, G. H. N. (2001). Inhibition of restriction enzyme’s DNA sequence recognition by PUVA treatment. Photochemistry Photobiology 74(2): 269-273.
Hassan, S. A., Barthwal, R., Padmadeo, S. R. & Barukab, O. M. (2014). Restriction inhibition assay: A qualitative and quantitative method to screen sequence specific DNA binder from herbal plants. Tropical Journal of Pharmaceutical Research 13(2): 267-273.
Hazarika, P. & Dutta, D. (2013). Traditional knowledge for using plant resources as tooth brushing stick (datun) by the indigenous communities of Assam, India. International Journal of Herbal Medicinal 6(6): 22-34.
He, D., Wang, M., Zhao, S., Shu, Y., Zeng, H., Xiao, C., Lu, C. & Liu, Y. (2017). Pharmaceutical prospects of naturally occurring quinazolinone and its derivatives. Fitoterapia 119:136-149.
Howlader, M. A., Farhana, R., Shapna, S., Mohammad, R. R., Shams-Ud-Doha, K.M., Rumana, M. & Apurba, S. A. (2011). Antimicrobial, antioxidant, and cytotoxic effects of methanolic extracts of leaves and stems of Glycosmis pentaphylla (Retz.). Journal of Applied Pharmaceutical Science 1(8):137-140.
Kamel, M. M., Zaghary, W. A., Al-Wabli, R. I. & Anwar, M. M. (2016). Synthetic approaches and potential bioactivity of different functionalized quinazoline and quinazolinone scaffolds. Egyptian Pharmaceutical Journal 15(3): 98-131.
Khameneh, B., Iranshahy, M., Soheili, V. & Bazzaz, B. S. F. (2019). Review on plant antimicrobials: a mechanistic viewpoint. Antimicrobial Resistence and Infection Control 8: 118. doi: 10.1186/s13756-019-0559-6
Kumar, A., Banerjee, N., Singamaneni, V., Dokuparthi, S. K., Chakrabarti, T. & Mukhopadhyay, S. (2018). Phytochemical investigations and evaluation of antimutagenic activity of the alcoholic extract of Glycosmis pentaphylla and Tabernaemontana coronaria. Natural Products Research 32(5), 582-587.
Leite, G. C., Neto, L. V. P., Gaudereto, J. J., de Maio Carrilho, C. M. D., Ross, F., Anna Sara Levin A. S. & Costa, S. F. (2015). Effect of antibiotics combination and comparison of methods of synergism in multiresistant Gram negative bacteria. Journal of Infectious Diseases and Therapy 3: 207. doi: 10.4172/2332-0877.1000207
Li, D-D., Xu, Y., Zhang, D-Z., Quan, H., Mylonakis, E., Hu, D-D., Li, M-B., Zhao, L-Z., Zhu, L-H., Wang, Y. & Jiang, Y. Y. (2013). Fluconazole assists berberine to kill fluconazole-fesistant Candida albicans. Antimicrobial Agents and Chemotherapy 57(12): 6016-6027.
Mat Salleh, K. & Latiff A. (2002). Tumbuhan Ubatan Malaysia. pp. 473, Bangi: Pusat Pengurusan Penyelidikan Universiti Kebangsaan Malaysia.
Mawardi, R., Rosmiati, M. S., Najihah, M. H., Mohd Aspollah, S., Gwendoline, C. L. E., Abdul Manaf, A. & Hazar Bebe, M. I. (2010). Alkaloids and sulphur-containing amides from Glycosmis citrifolia and Glycosmis elongata. Sains Malaysiana 39(3): 445-451.
Mohamed, M. A., Ghanem, H. M., Abd El-Ghaffar, N. F. & Mohamed, S. S. (2013). Biological evaluation and molecular docking of substituted quinazolinones as antimicrobial agents. Australian Journal of Basic and Applied Sciences 7: 263–274.
Mohd Kamal, L. Z., Mohd Hassan, N., Md Taib, N. & Soe, M. K. (2018). Graveoline from Ruta angustifolia (L.) Pers. and its antimicrobial. synergistic potential in erythromycin or vancomycin combinations. Sains Malaysiana 47(10): 2429-2435.
Monte, J., Abreu, A. C., Borges, A., Simões, L. C. & Simões, M. (2014). Antimicrobial activity of selected phytochemicals against Escherichia coli and Staphylococcus aureus and their biofilms. Pathogens 3(2): 473-498. doi:10.3390/pathogens3020473
Murugan, N. & Natarajan, D. (2016). Phytochemical, antioxidant and antibacterial activities of Glycosmis pentaphylla (Rutaceae) leaf extracts against selected multi-drug resistant bacteria. Journal of Chemical and Pharmaceutical Research 8(1): 737-744.
Rahalison, L., Hamburger, M., Hostettmann, K., Monod, M. & Frenk, E. (1991). Bioautographic agar overlay method for the detection of antifungal compounds from higher plants. Phytochemical Analysis 2:199-203.
Sreejith, P. S., Praseeja, R. J. & Asha, V. V. (2012). A review on the pharmacology and phytochemistry of traditional medicinal plant, Glycosmis pentaphylla (Retz.) Correa. Journal of Pharmacy Research 5(5): 2723-2728.
Tillequin F. (2007). Rutaceous alkaloids as models for the design of novel antitumor drugs. Phytochemistry Review 6: 65-79.
van Vuuren, S. & Viljoen, A. (2011). Plant-based antimicrobial studies - Methods and approaches to study the interactions between natural products. Planta Medica 77: 1168-1182.
Wang, J., Di, Y., Yang, X., Li, S., Wang, Y. & Hao, X. (2006). Hydroquinone diglycoside acyl esters from the stems of Glycosmis pentaphylla. Phytochemistry 67(5): 486-491.
Yang, G.-Z., Wu, Y. & Chen, Y. (2012). Alkaloids from the stems of Glycosmis pentaphylla. Helvetica Chimica Acta 95: 1449–1451.
Yu., C., Bo, Y., Jing, X., Tong, Z., Hua, F. & Guang-zhong, Y. (2012). Photo-activated DNA binding and antimicrobial activities of alkaloids from Glycosmis pentaphylla. Acta Pharmaceutica Sinica 47(12): 1646−1652.
Zhou, A., Kang, T. M., Yuan, J., Beppler, C., Nguyen, C., Mao, Z., Nguyen, M. Q., Yeh, P. & Miller, J. H. (2015). Synergistic interactions of vancomycin with different antibiotics against Escherichia coli: Trimethoprim and nitrofurantoin display strong synergies with vancomycin against wild-type E. coli. Antimicrobial Agents and Chemotherapy 59(1): 276-281.