Dear Marko,

The concentration of antibacterial and antifungal activities of Quassia undulata and Quassia amara extracts in vitro was 5 mg/ml. At a concentration of 5 mg/ml all extracts exhibited marked antibacterial and antifungal activities in most cases higher than the standard reference drugs included in the study:

http://www.ncbi.nlm.nih.gov/pubmed/15259916

In another example, ethanolic and water extracts of three macrophytes (roots); Echinochloa stagnina (Retz.) P. Beauv; Pistia stratiotes (L.) and Nymphaea lotus (L.) from El-Serw, Dakahlia, Egypt were studied to verify their antimicrobial activities against certain microbial isolates by using agar well diffusion method. Bi-fold dilution technique revealed that all the tested microorganisms showed susceptibility to moderate resistance against E. stagnina ethanolic extract, with minimum inhibitory concentrations (MICs) values varied between 78.125 and 625.00 μg/ml, while its water extract showed antimicrobial activities that were significantly reduced by almost 50% compared to the ethanolic one.

http://www.sciencedirect.com/science/article/pii/S1687428513000083

 in a third study,  27 plant species used in the traditional medicine of Cambodia were screened for in vitro antibacterial and antifungal activities. Thirty-three methanolic extracts were tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Mycobacterium smegmatis and Candida albicans. Screened by disk diffusion assay, the extracts showed antimicrobial activity especially on Gram-positive bacteria. None of the crude methanolic extracts showed activity against P. aeruginosa. Twenty-five selected extracts were evaluated using a micro-dilution test. Harrisonia perforata (roots) and Hymenodictyon excelsum (bark) exhibited a bactericidal effect against S. aureus at a concentration of 500 microg/ml. Azadirachta indica (bark), Harrisonia perforata (roots and stem) and Shorea obtusa (roots) exhibited a bactericidal effect against M. smegmatis at 250 microg/ml.

http://www.ncbi.nlm.nih.gov/pubmed/17963325

In a fourth study, fifteen cyanobacteria belonging to Anabaena, Nostoc, Scytonema and Microcystis species isolated from various aquatic and terrestrial habitats were

screened for antimicrobial activity. A disc diffusion assay was used to detect the antimicrobial activity of crude hydrophilic and lipophilic extracts as well as culture supernatants of cyanobacteria on solid agar medium. Methanolic extracts of Anabaena BT2, Nostoc Brf02, Nostoc Brf04 and Scytonema br1 at a concentration of 500 µg/disc showed prominent zone of inhibition against two Gram-negative bacteria (Pseudomonas sb1 and sb3). In liquid cultures addition of 500 µg/ml crude extracts produced 72-78 % growth inhibition of test bacteria. Out of all the cyanobacteria tested only the methanolic extract of Microcystis and chloroform fraction of Scytonema br1 showed significant anticyanobacterial activity against Anabaena BT2 and Nostoc pbr01 and antialgal activity against a green alga Bracteacoccus. In liquid cultures a concentration of 300 µg/ml of these extracts

produced 73-85 % growth inhibition of the test organisms. None of the culture filtrates showed any antimicrobial activity.

http://www.ijppsjournal.com/Vol4Suppl3/3968.pdf

In a fifth study, cyanobacteria was screened for antibacterial and antifungal activity. The following summarizes the results revealed from this study:

As the photoautotrophic prokaryotes, Cyanobacteria produce a variety of secondary metabolites that exhibited as antibiotics, allele-chemicals, hormones and toxins etc. Besides their specific feature of nitrogen fixation, toxic behavior has attracted to

biologists and various strains have been extensively studied by several workers and advocated their antimicrobial nature such as antibacterial, antifungal, antialgal, as well as allele-pathic & antagonistic properties. In the same direction, the assessment of toxicity of few local isolates (Anabaena iyengerii, Nostoc sphaerica, Microcystis aeruginosa, Oscillatoria boryana and Phormidium fragile) against three pathogenic bacteria (Escherichia coli, Mycobacterium ulcerance and  Staphylococcus epidermidis) and fungi (Aspergillus niger, Candida albicans and Rizoctonia solani) have been performed during present investigation. Crude extracts of two heterosystous and three nonheterocystous cyanobacteria have been examined, whereas the positive response was observed, especially nonheterocystous cyanobacteria showed great toxicity comparable to standard

antibiotics and fungicides res. Obviously the observation revealed that the cyanobacterial strains posses broad spectrum antimicrobial properties.

http://www.ijsr.in/upload/485559344Microsoft%20Word%20-%20LEC%201.pdf

in a sixth study,  a large number of antibiotic compounds, many with novel structures, have been isolated and characterised. Similarly many cyanobacteria have been shown to produce antiviral and antineoplastic compounds. A range of pharmacological activities have also been observed with extracts of microalgae, however the active principles are as yet unknown in most cases. Several of the bioactive compounds may find application in human or veterinary medicine or in agriculture. Others should find application as research tools or as structural models for the development of new drugs. The microalgae are particularly attractive as natural sources of bioactive molecules since these algae have the potential to produce these compounds in culture which enables the production of structurally complex molecules which are difficult or impossible to produce by chemical synthesis.

http://link.springer.com/article/10.1007/BF00003544

In a seventh study, the antibacterial and antifungal activity of callus culture (two different hormonal combination culture medium) and adult plants (two collect) extracts from Alternanthera maritima (Amaranthaceae) were in vivo and in vitro studied. The antibacterial and antifungal activity was determined by the agar-well diffusion method against thirty strains of microorganisms including Gram-positive and Gram-negative bacteria, yeasts and dermatophytes. All the organic crude extracts studied were bioactive. Extracts of aerial parts and roots of adult plants collected during the same period of years of 1995 and 1998 (Restinga de Maricá (RJ), collect 1 and 2) inhibited the growth of several microorganisms (bacteria, yeasts and dermatophytes) with inhibition halo between 6 and 20 mm. Plant cell callus culture extracts obtained from two culture conditions were also bioactive. Thus, the positive results suggest that the A. maritima extracts should be further studied to determine the bioactive chemical compounds as well as to understand the possible mechanisms of action and evaluate their toxicity looking toward a pharmaceutical employment.

http://www.scielo.br/pdf/bjm/v35n1-2/arq22.pdf

For the suppliers, please see the Materials & Methods sections in the above mentioned 7 articles.

Hoping this will be helpful,

Rafik

Dear Rafik,

Thanks for the mail. However, I am looking on available substances that can kill algae, cyanobacteria, bacteria and fungi without damage effects to plants in vitro.

Best,

Marko