famous commercial antimicrobial were found by big pharmaceutical industries (of course that pharmaceutical industries don't want reveal where they found those compounds) , and that antimicrobial are on patents.

We witness the end of the antibiotics era, you see MDR-microorganisms spread all over the world!. If the big pharmaceutical companies are part of the problem, means we are going to face a global disaster due to outbreaks of super bugs!

Well as Michael sad, there are numerous older papers that have the activity of diverse antibiotics! Also in most of new papers there are at least one standard (positive control)...also for all clinical isolates antibiograms are necesery to be done...

There are certainly many plants, and plant fractions and subfractions which have antimicrobial activity. The trick is to find the pure substance or substances which support the antimicrobial activity, define the range of antimicrobial activity, and determine the therapeutic index if used in vivo. Small questions, but quite important in order to identify potential new classes of antibiotics.

Thank you all for these fruitful discussion.

If you want something on that subject, pure plant components and their effects on microorganisms, try reading review form our research group published last year: 

Antimicrobial Plant Metabolites: Structural Diversity and Mechanism of Action.

You can download it from my RG profile, i think you it can be useful, let me know about your impressions :)

all best

Nikola

Thanks Nikola, I will read it and reply soon.

Many of the antimicrobial assays we perform seldom use pure isolated compounds from plants or nature for that matter. Many of the plant extracts work in synergy to give a particular activity, be it antibacterial of antifungal of other. However when some of these compounds are isolated and purified, they seldom have a more potent biological activity than the mixture. I think pharmaceutical companies  prefer working with highly purified mono-compounds. It is easier to work with them i suppose

At the moment, we have started running out of antimicrobial agents, because of antimicrobial resistance (mainly due to misuse of these agents).

This has made mainstream medicine increasingly receptive for the use of antimicrobial and other drugs derived from plants, as traditional antibiotics (products of microorganisms or their synthesized derivatives) become ineffective and as new, particularly viral, diseases remain intractable to this type of drug. Another driving factor for the renewed interest in plant antimicrobials in the past years has been the rapid rate of (plant) species extinction.

I dont know if I go to the point, but most of the antibiotics used for infections treaments come from bacteria and fungi and not from plants.

Really?!

Try for example for cephalosporin:

http://www.ncbi.nlm.nih.gov/pubmed?term=cephalosporin%20antibacterial%20activity&cmd=correctspelling

Yes, there are a large number of antimicrobials from plants.

One of the main reasons you find that commercial antibiotics are produced by microorganisms is because they are easier to use for production than plants or plant cells.

A microbe that produces an antibiotic can be manipulated to produce higher yields of the compound. Coupled with the higher growth rates of the microbe and their ability to be cultured in bioreactors in large volumes means that their products are more economic to produce. Commercial demand can therefore be met more readily than if the compound had to be extracted from the plant itself. Plant cell culture is an alternative, but yields and scale up remain the major bottleneck to commercial production.

we can look for antimicrobial activities on basis of two aspects in medicinal plants. 1- according to kind of group of chemical material e.g. thymol  which can control some microbs  , these material are exist in ajwan seed and thyme aerial parts. 2- according to kind of  plants e.g. mint family which have antimicrobs properties   

There is a difference between an antimicrobial compound isolated from a plant as well as an commercial antibiotic. Antibiotic is selectively generated by a microbe that produces that can be manipulated to produce higher yields of the compound. But natural compounds lack this production ability by artificial means because its template or gene transfer and expression are quite hard and different. Though these can be chemically synthesized in the laboratory. A bio-organic compound might have antimicrobial activity at least against two three microbes or series of microbes but an antibiotic has selectivity only for single microbe.

I think, as a scientists, most of us believe that antibiotics have no future!. Pharmaceutical companies are interested only in money!. For better future, researchers should search for new alternatives from plants, algae, bacteria fungi,....

Emad M. Abdallah true, they're so concerned with mass producing it and making lots of money, however, perhaps we can do synthesis to answer the problems on the yield. We only need lead compounds to guide us.