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/Ftable 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 https://www.datingranking.net/de/android-de activity prediction. 39
Brand new roentgen worth of 0.976 of model six shown there is actually a strong relationship involving the independent variables (descriptors) and you can cytotoxic factors of your own xanthones. I affirmed that 97.6% of the changed cytotoxic passion of your examined xanthones is actually caused by the modification away from qC1, qC2, qC3, second dipole, and logP. Hence, architectural modification is suggested towards band An effective or C. 41
The brand new correlation effect showed that model six you will predict the fresh cytotoxic activity of 10 xanthone compounds very well, with a mountain and you can correlation coefficient (Roentgen 2 ) regarding 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.
Might build off xanthone (Table step one) demonstrates that phenyl band B can’t be replaced. Customization of your own web charges from adjacent atoms (qO11, qC9, qC9a, qC4a, qO10, qC10a, and you will qC8) simply be purchased because of digital occurrence induction off charge modification regarding atoms when you look at the phenyl bands A beneficial and you can C. Based on the build regarding material 5 (as it encountered the greatest cytotoxic interest), that it modification is attained by modifications during the qC5, qC7, and you may qC8 (ring A) at qC1 and you will qC2 (band C). For this reason, both of these phenyl groups have to be thought inside the design a different xanthone with better 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.