In this study four plants (Chrozophora hierosolymitana Spreng, Chrysanthemum leucanthemum L., Ephedra gerardiana Wall. ex Stapf and Quercus dilatata L.) collected from different regions of Pakistan were screened to identify any chemotherapeutic agents present in them. Seven crude extracts of these plants (leaf, stem and root extracts of C. hierosolymitana, aerial parts of C. leucanthemum, stem and root extracts of E. gerardiana and aerial parts of Q. dilatata) were examined for antimicrobial activity using agar diffusion method and agar tube dilution method, cytotoxicity using brine shrimp assay, antitumor activity using potato disc assay, phytotoxic activity using radish seed bioassay and antioxidant activity by using DPPH radical scavenging assay and free radical induced oxidative DNA damage assay. Two plant extracts of C. hierosolymitana and Q. dilatata showed antibacterial activity. Two plant extracts of E gerardiana and C. leucanthemum showed antifungal activity. Two plant extracts i.e., leaf extract of C. hierosolymitna and root extract of E. gerardiana showed significant brine shrimp cytotoxicity activity (IC 50 171.55 to 523.8 ppm). Six of the seven extracts exhibited tumor inhibition at all the three concentrations tested ranging from 10 to 80%. All extracts showed significant plant growth and seed germination inhibition at higher concentrations against radish seeds. Two extracts of C. hierosolymitana and Q. dilatata showed growth stimulating effects at lower concentrations. Two extracts of C hierosolymitana and Q. dilatata showed significant DPPH radical scavenging activity (IC 50 10.52 to 45.9 ppm). Three of the seven extracts i.e., (R) E. gerardiana, (A) Q. dilatata and (A) C. leucanthemum showed DNA protection activity at 100 and 10 ppm while at 1000 ppm showed no DNA protection activity while rest of the four extracts showed DNA protection activity at all the three concentrations tested. Phytochemical tests showed presence of alkaloids, saponins, anthraquinones, terpenoids, flavonoids, flavones, tannins, phlobatannins and cardiac glycosides at varying levels in these extracts. The crude extract of the most active antibacterial plant extract (A) Q. dilatata was subjected to bio-guided fractionation. Six partitioned fractions of aerial parts of Q. ixdilatata were tested for antibacterial and antioxidant activities. Phytochemical analysis of these partitioned fractions was also done. Ethanol fraction was selected on the basis of results of bioassays and phytochemical analysis. This fraction was analyzed by RP- HPLC and seven fractions were collected. Out of the seven fractions, AM2 showed antioxidant activity while AM3 showed antibacterial as well antioxidant activity. These two active fractions were again analyzed by RP- HPLC. The subfractions AM3b and AM3c showed antibacterial activity while AM2b showed antioxidant activity. Purified active subfractions were charaterized by comparing their absorption spectra with that of standard natural products isolated from the plants of same genus. The absorption spectra of the active fractions were different from that of the standard compounds previously isolated from the Quercus genus suggesting that these are newly isolated compounds from this genus.