You can refer WHO guidelines for standardization plant material

If you want to do exhaustive extraction try to use solvents of different polarities (i.e. polar, moderately polar and apolar). If you need to extract polar compounds extract with water, methanol and/or ethanol (or mixtures) and mix the extracts. For medium polarity compounds extract  with some solventes as ethanol, 2-propanol, dimethyl sulfoxide (expensive, high boiling point, but a very good solvent), acetone, dichloromethane, chloroform, ethyl acetate and mix the extracts. If you need apolar compounds extract with less polar solvents: diethyl ether(or t-butyl methyl ether), toluene, hexane and mix the extracts. You can also, after concentrate in a rotavapor at low temperature, combine medium polarity and apolar compounds and dissolve in suitable solvents like DMSO, Chloroform, acetone or other mixtures. There are mixtures of solvents with good extraction properties such as chloroform/methanol for lipids. Considere that is better to do multiple extractions with small volumes than only one extraction with the whole volume and that there are several extraction methods, I suggest you to use ultrasonic assisted extraction.

Best Regards

See also: J. Agric. Food Chem., 2006, 54 (7), pp 2750–2753