10.22376/ijpbs.2019.10.1.p1-12 Volume 4 Issue 3 2013 (July - September) Investigations have been made to develop an efficient protocol for identification and quantification of phenolic acids and flavonoids in hairy roots (HR) of lessThan i greaterThan Hypericum perforatum lessThan /i greaterThan L. HR were induced from root segments of lessThan i greaterThan in vitro lessThan /i greaterThan grown seedlings from lessThan i greaterThan H. perforatum lessThan /i greaterThan , after co-cultivation with lessThan i greaterThan Agrobacterium rhizogenes lessThan /i greaterThan A4. Transgenic status of HR was confirmed by PCR analysis using lessThan i greaterThan rol lessThan /i greaterThan B specific primers. HR grew rapidly on hormone-free medium and had plagiotropic growth with vigorous production of lateral roots. Phenolic acids and flavonoids in control roots and HR were analyzed using HPLC/DAD/ESI-MS lessThan sup greaterThan n lessThan /sup greaterThan . Quinic acid was the only detectable phenolic acid in HR. Transgenic roots produced flavonol glycosides such as quercetin 6- lessThan i greaterThan C lessThan /i greaterThan -glucoside, rutin and isorhamnetin lessThan i greaterThan O lessThan /i greaterThan -hexoside. Chromatographic analysis of flavonoid aglycones in HR resulted in the identification of kaempferol. Transformed roots yielded higher levels of catechin and epicatechin than untransformed roots. lessThan i greaterThan H. perforatum lessThan /i greaterThan HR represent promising experimental system for enhanced production of phenolic compounds. OLIVER TUSEVSKI AND SONJA GADZOVSKA SIMIC Hypericum perforatum L., Agrobacterium rhizogenes A4, hairy roots, phenolic acids, flavonols, flavan-3-ols. 737-748