Nowadays the degree of dental caries and related problems are increasing with severe effects. As part of search for effective phytoderivatives against dental pathogens, Sida urens L., was collected and its fraction was applied against bacterial isolate. The result evidenced that Sida urens is with acceptable levels of bactericidal activity and showed good antibacterial activity as compared with that of standard drug Gentamicin.
The bacteriostatic and bactericidal activity could be ascribed to the presence of flavonoids and coumarin-related compounds. A probable degree of lipophilicity might be responsible for the polyphenol-rich fractions being higher in activity than Gentamicin. Lipophilicity toxicity is due to the interactions with the membrane constituents and their arrangement . The reason for the different activity between Gram-positive and Gram-negative bacteria could be accounted for by the morphological differences between these micro-organisms. Gram-negative bacteria have an outer phospholipidic membrane carrying the structural lipopolysacharide components. This makes the cell wall impermeable to lipophilic solutes while porins constitute a selective barrier to the hydrophilic. The Gram-positive bacteria become therefore more susceptible having only an outer peptidoglycan layer which is not an effective permeability barrier . Generally therefore, Gram-negative bacteria are more resistant than Gram-positive bacteria because of the complexity of the cell wall of Gram-negative bacteria . Results of antibacterial activity confirm again that the plant extracts inhibited the Gram-positive bacteria better than the Gram-negative ones. Moreover, the reason could be attributed to the presence of extra outer membrane in their cell wall acting as barrier for the compound(s) to diffuse into the bacterial cells . The findings demonstrated promising antibacterial activity of polyphenol-rich fractions from Sida urens. The zones of inhibition and bactericidal and bacteriostatic effect values suggest that this Malvaceae can significantly inhibit bacterial growth in a laver dose dictates its potential as a source of active chemicals that might be used for the discovery of new antibacterial agent. We presume that the presence of the natural antimicrobial compounds such as phenolic compounds from the plant. In effect, phenolic compounds as simple phenols and phenolic acids whose mode of action is via enzyme inhibition by the oxidized compounds, flavones, flavonoids and flavonols have the ability to complex with proteins and bacterial cell walls and tannins inactivate microbial adhesions, enzymes and cell envelope transport proteins . Therefore, the presence of flavonoids, phenolic in plants has been shown to be responsible for antimicrobial activity in plants . Their role is to protect plants against microbial or insect damage . Since medicinal plants contain pharmacologically active substances with antimycobacterial, antibacterial and antifungal properties , the antibacterial activity of the plants tested could therefore be attributed to the presence of these compounds.
The results of the present study indicated that the extract of Sida urens is not poisonous. During the 14 day period of acute toxicity evaluation, some signs of toxicity were observed, but they were all quickly reversible. Pharmacological substances whole LD
is less than 5 mg/kg body weight are classified in the range of highly toxic substances, those with a LD
between 5 mg/kg body weight and 5000 mg/kg body weight are classified in the range of moderately toxic substances and those with the lethal dose is more than 5000 mg/kg body weight not toxic. In this fact, if we refer to this classification we could say that the extract of Sida urens is not toxic and would be regarded as being safe .
The analgesic activity study revealed that polyphenol-rich fractions showed good activity compared with that of standard drug paracetamol. Acetic acid induced writhing in mice attributed visceral pain finds much attention of screening analgesic drugs . The polyphenol-rich fractions showed significant analgesic action compared to the reference drug. Pain sensation in acetic acid induced writhing method is elicited by triggering localized inflammatory response resulting release of free arachidonic acid from tissue phospholipid  via cyclooxygenase (COX) and prostaglandin biosynthesis . In order words, the acetic acid induced writhing has been associated with increased level of PGE2 and PGF2α in peritoneal fluids as well as lipoxygenase products . The increase in prostaglandin levels within the peritoneal cavity then enhances inflammatory pain by increasing capillary permeability . The acetic acid induced writhing method was found effective to evaluate peripherally active analgesics. The agent reducing the number of writhing will render analgesic effect preferably by inhibition of prostaglandin synthesis, a peripheral mechanism of pain reduction . The significant pain reduction of polyphenol-rich fractions might be due to the presence of analgesic principles acting with the prostaglandin pathways. The abdominal writhing induced by acetic acid was also reported to be less selective  and proposed to act indirectly by releasing endogenous mediators stimulating neurons that are sensitive to other drugs such as narcotics and centrally acting agents .
Therefore, it is assumed that these compounds may be responsible for the observed analgesic activity. Flavonoids were reported to have a role in analgesic activity primarily by targeting prostaglandins . There are also reports on the role of tannins in anti-nociceptive activity .