Antibacterial and antiviral proteins from Litchi chinensis seeds

Litchi chinensis fruits have been used in Brazilian popular medicine as antibiotic and anti-viral agent on the treatment against several diseases. Some plants possess proteins which presents inhibitory activity against microbe and virus. For this reason, we decide to investigate the presence of these proteins in the plant mentioned above. Crude extract from seeds was prepared using 0.1M NaCl, 0.01M HCl solution (1:5, w/v, meal to solution ratio) with continuous stirring during 2h. The material was centrifuged and the supernatant was precipitated with ammonium sulphate (0–90% saturation). This fraction, after dialysis against water, was used to determine the antibacterial activity against Rhodococcus equi and Staphylococcus aureus in a disk test (disk diffusion, solid culture media, 37°C for 48h). Protein quantification was done by Bradford [1] assay and disks containing 1.0 microg/mL of proteins were used. Distilled water was utilized as a negative control. After 48h, inhibition halos zones of 7–10mm of diameter were observed around the disks. On the antiviral assay was used the Herpes simplex virus. The protein fraction was able to inhibit the attack from H. simplex to bovine cells. The proteins were visualized in SDS-PAGE [2], indicating proteins with molecular mass between 18 kDa and 60 kDa. Ionic exchange chromatography was done by using CM-cellulose (HPLC-Akta, Superdex 75 column). Some of these proteins could be candidates to the production of antibiotic and antiviral products for applications in the human medicine and veterinary medicine.

Acknowledgements: EMBRAPA Cerrados, Planaltina -DF, Brazil, Marília Santos Silva.

References: [1] Bradford M. M., Anal Biochem. 1976;72: 248–54. [2] Laemmli U. K., Nature. 1970 Aug 15; 227(5259):680–5.