preferred_name: xanthine(out) + Na(+)(out) => xanthine(in) + Na(+)(in)
preferred_name_lc: xanthine(out) + na(+)(out) => xanthine(in) + na(+)(in)
label: xanthine(out) + Na(+)(out) => xanthine(in) + Na(+)(in)
label_lc: xanthine(out) + na(+)(out) => xanthine(in) + na(+)(in)