2.7 Molecular docking
In order to predict the possible interaction patterns between natural compounds and STAT3, molecular docking studies were carried out using Autodock 4.2 software (The Scripps Research Institute, La Jolla, CA, USA). The preparations related to Autodock docking were performed using the Autodock Tools (ADT). The three-dimensional (3D) crystal structure of STAT3 (PDB code: 1BG1) was retrieved from the RCSB Protein Data Bank (PDB; http://www.rcsb.org/pdb/). The standard 3D structures of natural compounds were constructed by using the “SKETCH” option function in SYBYL-X 2.1 (Tripos International, St. Louis, MO, USA). The Lamarckian genetic algorithm (LGA) was used to implement the molecular docking. The docking parameters were set as follows: population size, 150; number of generations, 270 000; number of evaluations, 25 000 000; number of top individuals that automatically survive, 20; and number of docking runs, 40. The default values of the remaining parameters were used.