preferred_name: a sphingoid base + a fatty acid => an N-acyl-sphingoid base + H2O
preferred_name_lc: a sphingoid base + a fatty acid => an n-acyl-sphingoid base + h2o
label: a sphingoid base + a fatty acid => an N-acyl-sphingoid base + H2O
label_lc: a sphingoid base + a fatty acid => an n-acyl-sphingoid base + h2o