The aerial parts of 16 Syrian medicinal plants related to Asteraceae and Lamiaceae families were extracted with petroleum ether, chloroform and ethanol. The yield of extracts (48 extracts) ranged between 1.42% in petroleum ether extract of Melissa officinalis to 22.55% in chloroform extract of Inula viscosa .
Phytochemical screening showed the presence of flavonoids and steroidal triterpenes in the most of tested extracts. saponins were not observed in any extract.
Antimicrobial activity screening at the concentration of 1 mg extract/1ml medium showed that 13 extracts related to 6 plants showed some degree of antimicrobial activity against at least one microorganism. Only Pseudomonas aeruginosa was resistant to all tested extracts in this research.
Antimicrobial activities of these extracts were determined by agar well diffusion method. 20, 40 or 80 microliters (µl) of the plant extract (at a concentration of 5%) were poured in the wells.
Most of tested extracts showed some Antimicrobial activities but the greatest activity was exhibited by the petroleum ether extracts of Thymus cilicicus and Origanum syriacum.
For instance when we used 80 µl of the petroleum ether extracts of Origanum syriacum the diameter of the inhibition zone was 52 mm for Staphylococcus aureus, 22.67 mm for Escherishia coli and 35 mm for Candida albicans.
Minimal inhibitory concentrations (MIC) were determined for the most active extracts. For instance MIC was 0.25 mg/ml for Staphylococcus aureus when we used chloroform extracts of Thymus syriacus.
In general the petroleum ether and chloroform extracts were more active than ethanol extracts.
Gram positive bacteria were more susceptible to tested plant extracts than gram negative bacteria.
The antimicrobial activity of Centaurea ptosimopappa and Inula graveolens has been reported here for the first time.
We have predicted during several field tours which included spring and summer of 2003- 2005 indivisuals of the species Centaurea ptosimopappa in the northern areas of Lattakia.
We have registered its existence in these sites: Fronlok, Ainelharamiyah, Ommuttoyour, and to the north of Fronlok in the direction of Kessab.
It drew our attention in nature and during the examination of samples in the Lab. That some morphological differences are essentially occurant between two groups of the individuals of this species without expressing geographic isolation in regards to its gathering sites, nevertheless they were detected growing side by side in several places especially in Ommuttoyour.
These morphological differences had been prominent in a few characteristics, they are:
1- Leaf Pilosity.
2- Stem Pilosity.
3- Color of Base Leaves (bluish green or whitish green).
4- Lamina (blade) of Base Leaves Shape (Oblong-Spatulate or Oblong-Linear).
5- Dimensions of Base Leaves (length, width, and the ratio of length/width).
6- Dimensions of Stem Leaves (length, width, and the ratio of length/width).
7- Dimensions of Heads (length, width, and the ratio of length/width).
The detection of the active constituents in the extracts of the individuals of these two groups of this species, and the yield of the extracts, and its antimicrobial activity enhanced (enforced) these differences between the two groups.
The multiplicity and the importance of different morphological characteristics and their reflex concerning active constituents and antimicrobial activity asserted the nomenclature of two subspecies are mentioned for the first time in our recent research:
Centaurea ptosimopappa Hayek nova subsp. glabra Bello(2005)
Centaurea ptosimopappa Hayek nova subsp. Canescens Bello(2005).
We have described the studied plants species and verified their scientific names definitely depending on modern Floras.
Plant species related to Asteraceae and Lamiaceae families have been defined as they were mentioned in the sources of the Arab scientific heritage. The most important of these are "Al-Qanoon" for Ibn-Sina, "Al-Jamie" for Ibn-Albitar and "Attathkara" for Al-Antaki. The Arabs used these plants in phytotherapy.
We have verified their scientific names, then we have made a well-planned comparative study of some chosen species concerning:
1- Comparison the nomenclature and plant description as mentioned in the sources of the Arab scientific heritage with those in the available Floras especially Post Flora and Mouterde Flora.
2- Comparison the traditional medical uses as they were stated in heritage sources with the modern uses as in the recent medicinal plant books and the latest scientific researches in the field of herbal medicine.
The most important results that we extracted in this matter:
1- Some medicinal plants which the Arab physicians and herbalists used in the past are no longer used now neither in folk medicine nor in modern herbal medicine (they were not studied in the recent researches), some of these forgotten plants are: Lycopus europaeus and Phlomis spp. From Lamiaceae, Ambrosia maritime, Anacyclus pyrethrum, Aster tripolium, Chondrilla juncea, Onopordon spp., Tragopogon pratensis and Xanthium spinosum from Asteraceae.
2- Some plants are still have the same old uses, these can be divided into two types:
a- plants that their properties have have been proved, for instance: Antitussive and Antispasmodic activity for Thymus spp. and Antidepressive for Meliss officinalis.
b- Plants used in folk medicine without making sure of their activities clinically or scientifically, for instance:
3- Some other plants were early used to treat some diseases, but some new bioactivities have been discovered recently, especially concerning Antimicrobial activity for Inula viscosa, Antioxidant activity for Origanum vulgare and Hypoglycemic activity for Cichorium intypus.
4- Some other plants were not used in the past and they have been added to the list of medicinal plants lately and/or some bioactivities have been reported for them recently, such as: Echinacea purpurea and Centaurea ptosimopappa.
We have proved or refused the old uses for the chosen plants and asserted the best medical uses. These uses that were mentioned in the Arab scientific heritage sources and they have been proved lately in our recent research and/or other modern researches.
Keywords: Antimicrobial activity, Phytochemical screening, Plant extracts, Lamiaceae, Asteraceae, Syrian Medicinal Plants, Centaurea ptosimopappa, Pilosity, Oblong-Spatulate, Oblong-Linear, Heads, subsp. glabra Bello(2005), subsp. Canescens Bello(2005), Arab scientific heritage, Al-Qanoon" for Ibn-Sina, "Al-Jamie" for Ibn-Albitar, "Attathkara" for Al-Antaki, phytotherapy, herbal medicine, Post Flora, Mouterde Flora, herbalists, Antioxidant activity, Hypoglycemic.