Antiviral screening of four plant extracts against acyclovir resistant herpes simplex virus type-1.

Herpes simplex virus type 1 (HSV-1) causes serious infections particularly in immunocompromised patients. Methanolic extract of four plants were evaluated for their anti-viral effects against acyclovir resistant HSV-1 in HeLa cell line. The 50% cytotoxic concentration (CC50) as well as the effective minimal cytotoxic concentration of each plant extract were evaluated by MTT assay. Antiviral effects of the plant extracts on HSV-1 were examined at different concentrations of the extract. The effective minimal cytotoxic concentration was evaluated at different times of virus replication after infection. Virus titration was assessed by tissue culture infectious dose 50 (TCID50) method. Among the 4 plant extracts evaluated only Mentha pulegium L. extract was shown to exert the highest antiviral activity, with selectivity index (SI) 10.25. Direct treatment of HSV-1 with Mentha pulegium L. extract resulted in 1.7 log10 TCID50 reduction in virus titers after one hour. The highest reduction in HSV-1 infectivity was obtained 1 hour after the infection of the cells with virus resulting in 2.1 log10 TCID50 reduction as compared to the control. The antiviral effects of Mentha pulegium L. extract on HSV-1 after virus infection was more remarkable than the virucidal activity.

Effects of Piriformospora indica and Sebacina vermifera on growth and yield of essential oil in fennel (Foeniculum vulgare) under greenhouse conditions.

Fennel (Foeniculum vulgare) is a very important plant in the family of Apiaceae. Effects of inoculation of two endophytic fungi (Piriformospora indica and Sebacina vermifera) in growth, yield and composition of the essential oil of fennel (F. vulgare) were evaluated in pot cultures. Dry fruits were ground with an electric grinder and oil was extracted by hydrodistillation, and their composition was determined by GC/MS. In pot experiment, the maximum dry weight of the green tissue and root and plant height were obtained with P. indica, and maximum number of umbels per plant and dry weight of 1000 fruits were produced with S. vermifera. The P. indica and S. vermifera inoculation significantly increased oil yield as compared to non-inoculated control plants. GC and GC/MS studies revealed that the level of anethole was increased with P. indica and S. vermifera.

Effect of Matricaria chamomilla L. flower essential oil on the growth and ultrastructure of Aspergillus niger van Tieghem.

The antifungal activity of Matricaria chamomilla L. flower essential oil was evaluated against Aspergillus niger with the emphasis on the plant's mode of action at the electron microscopy level. A total of 21 compounds were identified in the plant oil using gas chromatography/mass spectrometry (GC/MS) accounting for 92.86% of the oil composition. The main compounds identified were alpha-bisabolol (56.86%), trans-trans-farnesol (15.64%), cis-beta-farnesene (7.12%), guaiazulene (4.24%), alpha-cubebene (2.69%), alpha-bisabolol oxide A (2.19%) and chamazulene (2.18%). In the bioassay, A. niger was cultured on Potato Dextrose Broth medium in 6-well microplates in the presence of serial two fold concentrations of plant oil (15.62 to 1000 microg/mL) for 96 h at 28 degrees C. Based on the results obtained, A. niger growth was inhibited dose dependently with a maximum of approximately 92.50% at the highest oil concentration. A marked retardation in conidial production by the fungus was noticed in relation to the inhibition of hyphal growth. The main changes of hyphae observed by transmission electron microscopy were disruption of cytoplasmic membranes and intracellular organelles, detachment of plasma membrane from the cell wall, cytoplasm depletion, and complete disorganization of hyphal compartments. In scanning electron microscopy, swelling and deformation of hyphal tips, formation of short branches, and collapse of entire hyphae were the major changes observed. Morphological alterations might be due to the effect on cell permeability through direct interaction of M. chamomilla essential oil with the fungal plasma membrane. These findings indicate the potential of M. chamomilla L. essential oil in preventing fungal contamination and subsequent deterioration of stored food and other susceptible materials.

Inhibitory effects of Satureja hortensis L. essential oil on growth and aflatoxin production by Aspergillus parasiticus.

In an effort to screen the essential oils of some Iranian medicinal plants for novel aflatoxin (AF) inhibitors, Satureja hortensis L. was found as a potent inhibitor of aflatoxins B1 (AFB1) and G1(AFG1) production by Aspergillus parasiticus NRRL 2999. Fungal growth was also inhibited in a dose-dependent manner. Separation of the plant inhibitory substance(s) was achieved using initial fractionation of its effective part (leaf essential oil; LEO) by silica gel column chromatography and further separation by reverse phase-high performance liquid chromatography (RP-HPLC). These substances were finally identified as carvacrol and thymol, based on the interpretation of 1H and 13C NMR spectra. Microbioassay (MBA) on cell culture microplates contained potato-dextrose broth (PDB) medium (4 days at 28 degrees C) and subsequent analysis of cultures with HPLC technique revealed that both carvacrol and thymol were able to effectively inhibit fungal growth, AFB1 and AFG1 production in a dose-dependent manner at all two-fold concentrations from 0.041 to 1.32 mM. The IC50 values for growth inhibition were calculated as 0.79 and 0.86 mM for carvacrol and thymol, while for AFB1 and AFG1, it was reported as 0.50 and 0.06 mM for carvacrol and 0.69 and 0.55 mM for thymol. The results obtained in this study clearly show a new biological activity for S. hortensis L. as strong inhibition of aflatoxin production by A. parasiticus. Carvacrol and thymol, the effective constituents of S. hortensis L., may be useful to control aflatoxin contamination of susceptible crops in the field.