Complex sentence: Commercial varieties of potatoes are screened for solanine levels, and most have a solanine content of less than 0.2 mg/g. However, potatoes that have been exposed to light and started to green can show concentrations of 1 mg/g or more.
Split into simpler sentences: Commercial varieties of potatoes are screened for solanine levels, and most have a solanine content of less than 0.2mg/g. However potatoes that have been exposed to light and started to green can show concentrations of 1mg/g or more.