10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 2 2012 (April - June) The steroids of the brown alga lessThan i greaterThan Turbinaria conoides lessThan /i greaterThan were recognized as having mild-to-moderate cytotoxicity in HeLa cell, as it is being investigated towards determination of toxicity with various drugs. The cytotoxicity in HeLa cells was expressed in terms of 50% cytotoxic concentration (CC lessThan sub greaterThan 50 lessThan /sub greaterThan ). These oxygenated steroids exhibited cytotoxicity against HeLa cells with CC lessThan sub greaterThan 50 lessThan /sub greaterThan values ranging from 60.9 µg/mL to greaterThan 100 µg/mL. To analyse for their cytotoxicity, Quantitative structure activity relationship (QSAR) study was performed. It was done by multiple regression analysis with simulated annealing method of partial least square (PLS) model. A PLS model (r lessThan sup greaterThan 2 lessThan /sup greaterThan = 0.90, q lessThan sup greaterThan 2 lessThan /sup greaterThan = 0.80, pred_r lessThan sup greaterThan 2 lessThan /sup greaterThan = 0.96) was used as a base of consensus prediction of cytotoxicity. QSAR studies indicated the carbon atom (T_C_O_4: 12%) and any atom (T_2_2_7: 15%) away from the oxygen and double bond respectively, atomic valence connectivity index-order 0 (chiV0: 50%) and distance between most hydrophobic and hydrophilic point on the VanderWaals surface (XAMostHydrophobicHydrophilic distance: 20%) correlating well with mild cytotoxicity while the partial charges of the molecules (dipole moment: 25%) contributing moderate cytotoxicity. The 3D QSAR model further described that less bulkier substituent is required at steric site S_2441. Thus it can be concluded from the present study that cytotoxicity can be achieved by modifying the aromatic ring and preferring less bulky group to reduce steric hindrance. S.Sadish Kumar And Jayendra Turbinaria conoides, oxygenated steroids, cytotoxicity, QSAR 204-212