J. Drug Res. Egypt, Vol. 31, No.1 (2011) 32 Biotechnological and phytochemical Studies on Myrtus communis L. Including Determination of Essential Oil Content and antioxidant Activity. Mohammad M.EL-Zefzafy, Gouda T. M. Dawoud*. Adel E .Hegazy** National Organization for Drug Control and Research (NODCAR) Medicinal Plants Dept., * Phytochemistry Dept. Applied Research for Medicinal Plant Center (NODCAR). ** Genetic Engineering and Biotechnology Research Institute (GEBRI), Sadat City, Menufiya University Abstract: Shoot tips and nodes of Myrtle (Myrtus communis L family myrtaceae) were used as explants for callus formation in this study. Half salt strength of MS medium without plant growth regulators showed no callus formation and regeneration. The results clearly showed that half salt strength of MS basal solid medium supplemented with 1.0 mg/l NAA and 1.0 mg/l TDZ or 1.0 mg/l NAA and 1.0 mg/l BAP recorded the best results in callus production from shoot tip or node explants (5.29, 4.98, 3.84 and 3.69, mg /jar fresh weights, respectively). The same trend was obtained with the other parameters as 0.37, 0.35, 0.51 and 0.48 g / Jar dry weights, respectively, 98.66, 97.33, 63.55 and 54.29, callus percentage, respectively, 5.0, 4.85, 4.35, and 4.15, callus size (Degree) respectively. In regeneration, half salt strength of MS solid medium contained 1.0 mg/l IAA, 0.5 mg/l BAP and 0.2 mg/l GA3 observed the highest records in that concern with callus obtained before from both types of explant (shoot tips or nodes) in the medium contained 1.0 mg/l BA and 1.0 mg/l NAA. In acclimatization, shoots without in vitro root formation were transferred to soil mixture of equal volumes of peat-moss and sand. The highest percentage of survival was recorded when these shoots were dipping in solution of 1.5 mg/l IBA and 1.0 mg/l GA3. The quantity of essential oil of plant was equal 0.5 % (V/W) of yellowish volatile oil, from analysis of the oil using GC and GC/MS; it was obvious that it contained 14 compounds where α- pinene represented the highest percentage (66%) while α - thugen was the lowest one (0.5 %). The antioxidant activity was investigated in leaf extracts of in vitro produced plants and in vivo grown plants (mother plants) which recorded 82% and 75 % respectively. Total phenolic compounds and total flavoniodal contents were investigated in leaf extracts of in vitro produced plants and in vivo grown plants (mother plants) parameters were 112 μg% and 125 μg %, respectively with the extract of in vitro leaves while the extract of in vivo leaves (mother plants) showed 102 μg % and 114 μg %, respectively. Key words: - Myrtus communis L., myrtaceae, callus formation, regeneration, acclimatization, essential oil analysis, antioxidant activity, total flavoniod and plyphenol. INTRODUCTION Family myrtaceae contains about 80 genera and 3000 species which distributed in all the World. Myrtle ( Myrtus communis L family myrtaceae), a plant that in folk medicine has been used as anti-inflammatory drug, the plant is rich in polyphenols, galloyl-glucosides, ellagitannins, galloyl-quinic acids and flavonol glycosides, (Romani et al., 2004). The berry extracts of Myrtus communis L contains flavonoids and anthocyanins, the myrtle extract showed interesting free-radical scavenging activity (Montoro et al., 2006). Free radicals contribute to more than one hundred disorders in humans including atherosclerosis, arthritis, ischemia, reperfusion injury of many tissues, central nervous system injury, gastritis, cancer and AIDS. (Cook and Samman, 1996). Currently available synthetic antioxidants like butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT), tertiary Corresponding auther: melzefzafy@yahoo.com butylated hydroquinone and gallic acid esters, have been suspected to cause or prompt negative health effects. Hence, strong restrictions have been placed on their application and there is a trend to substitute them with naturally occurring anti- oxidants. Moreover, these synthetic antioxidants also showed low solubility and moderate antioxidant activity (Barlow, 1990). Myrtus communis L is a drought-tolerant evergreen shrub that can be used as an ornamental hedgerow or as a flowering potted plant (Holcomb and Michalas, 1992) Five broad classes of plant growth regulators are important in plant tissue culture: the auxins, cytokinins, gibberellins, abscisic acid and thidiazuron (Skoog and miller, 1957, Krishnamurthy, 2001 and Olszewski, 2002), plant growth regulators are one of the most important factors affecting cell growth, differentiation and metabolite formation in plant cell and tissue cultures (Rokem and Goldberg, 1985 and Liang, et al., 1991). MS medium with plant growth regulators was used for both shoot proliferation and rooting. The highest shoot formation (rapid clonally propagation) of a local Myrtle was achieved in vitro using tips excised from vegetative shoots outdoor-grown plants.