Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more  or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.  [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography .  : 10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. 
Constituents of the colocynth fruit and leaves ( Citrullus colocynthis ) include cucurbitacins.   The 2-O-β-D- glucopyranosides of cucurbitacins K and L can be extracted with ethanol from fruits of Cucurbita pepo cv dayangua .  Pentanorcucurbitacins A and B can be extracted with methanol from the stems of Momordica charantia .  Cucurbitacins B and I, and derivatives of cucurbitacins B, D and E, can be extracted with methanol from dried tubers of Hemsleya endecaphylla . 
This, of course, has all suddenly changed with the appearance of OPALS TM . An astute landscaper can now look over a customer's yard and with a high degree of reliability, give the entire landscape a numerical ranking. Actually, any landscape that would rank out at 5 or less, would be considered to be a fairly low allergy landscape; but in the near future, many customers may demand gardens that rate even better, 4s, or 3s, or even lower. It is actually possible to create an entire landscape now, from the lawns to the trees, that ranks out at 1. Such a landscape would in effect be completely pollen-free, and would also not pose any risks from contact allergy, or from what allergists often refer to as negative odor challenges.