Esters progressive identification

Fig. 5.6 Progressive identification of esters in roasted coffee volatiles...

Extraction and Identification. Identification of PE as the clearing enzyme in citrus juices progressed rapidly after MacDonnell et al. (17) reported on cation requirement for extraction and solubilization of the enzyme from various portions of the fruit. PE was assayed by the method introduced by Kertesz (18) and modified by Lineweaver and Ballou (19). The method involved measuring the rate at which the methyl ester groups in the pectin molecule are hydrolyzed by titrating the free carboxyl groups with 0.1N NaOH as they are formed. One unit of PE was defined as the amount of enzyme which will hydrolyze 1 meq carboxyl groups per min from a 0.5% solution of pectin in 0.15M NaCl at pH 7.5, 30°C (86°F). McDonnell et al. (17) showed that the enzyme... 

The 4,7-oxaeunicellane skeleton of the eleutherobins is also found in the eleuthosides (2, 3), the sarcodictyins (4), and the valdivones (5) (Figure 1) [4-6]. While the arabinosyl residue is not required for an antitumor effect, the methylurocanic acid ester side chain bound to C8 is part of the pharmacophore. Recent progress in the total synthesis of eleutherobin is discussed together with the identification of a common pharmacophore for tubulin-binding natural products, and a combinatorial way to determine the structure/activity relationship and drug optimization. 

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