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