Working on the framework of Relativistic Mean Field theory, we exposed the effect of nonlinear isoscalar-isovector coupling on G2 parameter set on the density dependence of nuclear symmetry energy in infinite nuclear matter. The observables like symm
etric energy and few related coefficients are studied systematically. We presented the results of stiff symmetry energy at sub-saturation densities and a soft variation at normal densities. Correlation between the symmetric energy and the isoscalar-isovector coupling parameter fully demonstrated for wide range of density. The work further extended to the octet system and showed the effect of coupling over the equation of state.
