Charges which are sources of fields must be universally conserved. Any quantity which is proved to be violated in certain circumstance cannot be a source of field. To account for the asymmetry of our universe baryon number A (or/and lepton number L) has to be violated thus A cannot be a charge. We speculate a new interaction MC with (A-L) as charge and Z* as messenger. Conservation of (A-L) instead of (3A-L) suggested by Sakharov was deduced on one hand from observational fact (our universe is both material and neutral) and on the other hand from the generalized Gell-Mann and Nishijima formula. Conservation of (A-L) forbids neutrinoless double beta decay and neutron antineutron oscillations. The union of four interactions electromagnetism, MC interaction, weak interaction and strong interaction considered as the product U(1) x U(1) x SU(2) x SU(3) would account for available experimental and observational data. Observation of processes violating baryon number would be of great interest to falsify this suggestion.