In this model, n represents the number of compounds contributed to build the model. The R value is the correlation coefficient; the closer R is to 1, the better the goodness of fit of the equation. 39 The Fcalc/Fdining table value represents the ratio between the variance of the calculated and tabulated values and, therefore, indicates that the regression relationships were statistically significant and did not occur by chance. Q2 serves as a criterion of robustness and predictive ability of the regression equation. The high Q2 value (>0.5) suggests the model’s ability to give an accurate prediction. The low s (the standard error of estimates) and SPRESS values suggest that the model is statistically significant for activity prediction. 39
The new roentgen value of 0.976 away from design 6 exhibited that there was a robust correlation within separate details (descriptors) and cytotoxic items of one’s xanthones. I verified one 97.6% of one’s altered cytotoxic passion of your learned xanthones try brought about of the modification of qC1, qC2, qC3, time dipole, and you may logP. Thus https://www.datingranking.net/es/citas-crossdresser, architectural modification is recommended towards ring A great or C. 41
The new relationship influence showed that design six you certainly will anticipate the newest cytotoxic hobby regarding 10 xanthone compounds well, with a hill and relationship coefficient (Roentgen dos ) of 0
Model 6 has been used to predict the activity of the compounds to enable comparison with experimental results (observed activity). Observed versus predicted log 1/ICfifty values based on the selected model 6 are presented in Table 6, and its scatter plot is presented in Figure 1. 976 and 0.951, respectively.
The essential construction regarding xanthone (Dining table step one) suggests that phenyl ring B cannot be replaced. Modification of your internet charges regarding surrounding atoms (qO11, qC9, qC9a, qC4a, qO10, qC10a, and you may qC8) will be purchased through electronic thickness induction off charges modification off atoms from inside the phenyl bands A and you can C. Using the framework out of compound 5 (since it met with the most readily useful cytotoxic activity), this modification might be attained by modifications from the qC5, qC7, and you may qC8 (band A beneficial) and at qC1 and you may qC2 (ring C). Therefore, both of these phenyl rings must be considered in the designing a special xanthone having best cytotoxic interest. 41
The best selected QSAR model is used to predict the cytotoxic activities of new synthetic xanthone compounds. The better cytotoxic activities of xanthones as IC50 values are given by the more positive value of log 1/IC50. Modification of new xanthones on the basis of the selected model 6 was performed by using the structure of compound 5 (3,4,6-trihydroxyxanthone) as the model because of the highest value of the cytotoxic activity. The more negative net atomic charge of qC1, qC2, and qC3, along with the more positive value of the dipole moment and logP, was recommended to increase the more positive value of log 1/IC50. Efforts such as substitution of electron-donating groups, such as R, OH, OR, NH2, NR2, NHCOR, OCOR, or CHCR2 groups, at the C1 and C2 positions (C3 position remained unchanged as the previous structure of compound 5) could be made. Structural modifications of compound 5 generated some formulas of new xanthones with better predicted cytotoxic activities, as listed in Table 7.
Table 7 The newly designed xanthone derivatives and their predicted cytotoxic activities calculated by using the best QSAR modelAbbreviations: IC50, inhibitory concentration 50%; QSAR, quantitative structure–activity relationship.