Proximate content, in vitro antioxidant and antimicrobial activity of Eulophia hereroensis Celine Mukakalisa 1 , Renate H Hans 2 , Kathithileni M Kalili 2 , Martha A Kandawa-Schulz 1 , Mervyn Beukes 3 , Vinesh Maharaj 4 1 Department of Biochemistry, Microbiology and Biotechnology, University of Namibia, Namibia, 2 Department of Physics, Chemistry and Material Science, University of Namibia, Namibia, 3 Department of Biochemistry, Stellenbosch University, South Africa, 4 Department of Chemistry, University of Pretoria, South Africa Eulophia hereroensis belongs to the Orchidaceae family, which although extensively studied worldwide, little is known about the nutritional and medicinal values of Southern African orchids. This study aimed to evaluate the macronutrient content, in vitro antioxidant, cytotoxic, antimicrobial and antibiofilm activities and also to identify phenolic compounds present in of the plant's tuberousextracts. Proximate analysis of the tubers revealed a high total carbohydrate content (88±0.85 g/100 g dry mass). Antimicrobial activity using the disc agar diffusion method against four microbial strains: Candida albicans, Klebsiella pneumonia , Escherichia coli and Staphylococcus aureus , displayed moderate antimicrobial activity fordichloromethane (DCM) extract. Antibiofilm activity against S. aureus , using the crystal violet assay, exhibited moderatebiofilm inhibitory and reduction activities forDCM extract . The antioxidant activity was evaluated using the DPPH radical scavenging, hydrogen peroxide radical scavenging, and reducing power assays. Although less active than the positive control, ascorbic acid, methanol extract showed strong DPPH and H 2 O 2 radical scavenging ability with IC 50 values of 0.056 and 0.041±0.003 mg/mL, respectively. Evaluation of the cytotoxicity effect of the extract on Vero and HT-29 cell lines, using the MTT assay, showed that E. hereroensis is not toxicand displayed a 42% growth inhibition of HT-29 cancer cells at high concentration. UPLC-MS allowed for a tentative identification of a caffeic acid-O-hexoside derivative from partially purified methanolic extract. The antimicrobial, antioxidant and cytotoxic activities of the extracts of this Namibian tuberous vegetable are reported here for the first time. Overall, the results obtained demonstrate the potential of E. hereroensis tubers to serve as functional food. Full characterization of the phenolic compounds using NMR spectroscopy as well as the confirmation of their in vitro and in vivo antioxidant activities, are recommended. References 1. Abidi, S.H., Ahmed, K., Sherwani, S.K., and Kazmi, S.U. (2014). Reduction and removal of Pseudomonas aeruginosa biofilm by natural agents. International Journal of Chemical and Pharmaceutical Sciences , 5(1): 28 – 34. 2. Josipović A., Sudar, R., Sudarić, A., Jurković, V., Kocãr, M.M. and Kulundzic, A.M. (2016). Total phenolic and total flavonoid content variability of soybean genotypes in eastern Croatia. Croatian Journal of Food Science and Technology , 8(2): 60 – 65. 3. Kapewangolo P., Omolo J. J., Bruwer R., Fonteh P. and Meyer D. (2015). Antioxidant and anti-inflammatory activity of Ocimum labiatum extract and isolated labdane diterpenoid. Journal of Inflammation , 12(4): 1-13. 4. Mutalin, L.Y., Nuraddin, S.M., and Aka, S.I. (2015). Phytochemical screening, antibacterial and antibiofilm evaluation of Lagenaria siceraria fruit growing in Kurdistan region\Iraq. Journal of Pharmacognosy and Phytochemistry , 4(1): 45 – 49. 5. Saeed N., Kham M.R., and Shabbir M. (2012). Antioxidant activity, total phenolic and total flavonoids contents of whole plant extracts Torilis leptophylla L. BMC Complementary and Alternative Medicine , 12: 221.
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