import re
p = r'(?<!\S)(standard|of|total|sum)(?!\S)'
s = '10-methyl-Hexadecanoic acid of total fatty acids'
print([x.strip() for x in re.split(p,s) if x.strip()])
aW1wb3J0IHJlCnAgPSByJyg/PCFcUykoc3RhbmRhcmR8b2Z8dG90YWx8c3VtKSg/IVxTKScKcyA9ICcxMC1tZXRoeWwtSGV4YWRlY2Fub2ljIGFjaWQgb2YgdG90YWwgZmF0dHkgYWNpZHMnCnByaW50KFt4LnN0cmlwKCkgZm9yIHggaW4gcmUuc3BsaXQocCxzKSBpZiB4LnN0cmlwKCldKQ==