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The measurement of the apsidal motion in close eccentric massive binarysystems provides essential information to probe the internal structure of thestars that compose the system. Following the determination of the fundamentalstellar and binary parameters, we make use of the tidally induced apsidalmotion to infer constraints on the internal structure of the stars composingthe binary system HD152219. The extensive set of spectroscopic, photometric,and radial velocity observations allows us to constrain the fundamentalparameters of the stars together with the rate of apsidal motion of the system.Stellar structure and evolution models are further built with the Cl\'es codetesting different prescriptions for the internal mixing occurring inside thestars. The effect of stellar rotation axis misalignment with respect to thenormal to the orbital plane on our interpretation of the apsidal motion interms of internal structure constants is investigated. Made of an O9.5 IIIprimary star (M1 = 18.64+/-0.47M${_\odot}$, R1 = 9.40+0.14-0.15R${_\odot}$,Teff,1 = 30900+/-1000 K) and a B1-2 V-III secondary star (M2 =7.70+/-0.12M${_\odot}$, R2 = 3.69+/-0.06R${_\odot}$, Teff,2 = 21697+/-1000 K),the binary system HD152219 displays apsidal motion at a rate(1.198+/-0.300){\deg}yr-1. The weighted-average mean of the internal structureconstant of the binary system is inferred: k2 = 0.00173+/-0.00052. For theCl\'es models to reproduce the k2-value of the primary star, a significantenhanced mixing is required, notably through the turbulent mixing, but at thecost that other stellar parameters cannot be reproduced simultaneously. Thedifficulty to reproduce the k2-value simultaneously with the stellar parametersas well as the incompatibility between the age estimates of the primary andsecondary stars are indications that some physics of the stellar interior arestill not completely understood.

Apsidal motion in massive eccentric binaries in NGC 6231: The case of HD 152219