Barking, ring

So far the Sinapis story can be interpreted as follows The shoot apical meristem of 2-month-old plants is presumably cytokinin-limited. Exposure to LD causes the production, in the leaves, of a signal which is then transported to the root system. There it alters the course of cytokinin metabolism and/or release. The increase in cytokinin levels in the transpiration stream (xylem) causes an increase in leaf cytokinin levels by 16 h. Some of the leaf cytokinins are then re-exported in the phloem sap to the apical meristem, where they cause a mitotic activation at 26-30 h. Since the cytokinin level in root exudate is altered as early as h 9 (Fig. 2), the initial leaf-to-root signal is apparently produced and transported extremely rapidly, i.e. within the first hour of the photo-extension period of the LD. The nature of this signal is unknown, but bark-ringing experiments indicate that it moves in living tissues (Lejeune, unpublished). 

Derivatives. Many derivatives of acylated phlorogluciaols that bear a benzene ring substituent or an ether or glycoside linkage occur ia aature. Examples are cotoia [479-21-0] (52) ia coto bark and conglomerone [480-25-1] (53) ia Eucalyptus conglomerata. 

The answer is c. (Hardman, pp 1260—1262.) Paclitaxel is a large structural molecule that contains a 15 membered taxane ring system. This anti cancer agent is an alkaloid derived from the bark of the Pacific yew tree. Its chemotherapeutic action is related to the microtubules in the cell. Paclitaxel promotes microtubule assembly from dimers and causes microtubule stabilization by preventing depolymerization. As a consequence of these actions, the microtubules form disorganized bundles, which decreases... 

Two new pseudotabersonine-related alkaloids were isolated by Husson et al. from the stem bark of T. albiflora from French Guiana (29) and characterized as (20/ )-18,19-dihydroxypseudovincadifformine (166, C2iH26N204, MP 190°C, [a]D +264°) and 19-hydroxy-20-epipandoline (167, C21H26N204, MP 204°C, [a]D +511°. Both compounds exhibited similar UV maxima attributed to a (3-anilinoacrylic chromophore, and their mass spectra showed, in addition to a molecular ion at m/z 370, a base peak at m/z 156 formed by retro-Diels-Alder fragmentation in ring C, followed by C-6—C-5 bond cleavage. 

Deplancheine (7) was isolated first from the stem and bark of Alstonia deplanchei van Heurck and Muell. Arg. by Husson et al. (14). The structure of this novel type of alkaloid has been established from spectral evidence the trans annellation of rings C and D is supported by the presence of characteristic Bohlmann bands in the IR spectrum and also by the chemical shift of the C-3 proton below 3.7 ppm. The ethylidene side chain was also indicated by the H-NMR spectrum [8 1.52 (3H, d, J =6 Hz), 5.30 (1H, q, J = 6 Hz)] and its E configuration was confirmed by regio- and stereospecific total synthesis (14). 10-Methoxydeplancheine (8) has been found in the leaves of Alstonia lanceolifera... 

Ahond et al. recently reported the isolation of two epimeric /V-oxides of 10-methoxydihydrocorynantheol from the trunk bark of Ochrosia moorei (26). The absolute configuration of the stereo centers at the annellation of rings C and D are 35,4/ in 26 and 35,45 in 27. 

Since the configuration at C-16 is undetermined, both quaternary alkaloids diploceline and 16-epidiploceline, isolated from the root bark of Strychnos goss-weileri Exell (54), could be represented by formula 50. The absolute configurations of the C-3 and C-15 have been determined by CD measurements, and the cis junction of C/D rings is supported by H-NMR data [8 4.58 (C3—H), 8 3.58 (N—CH3) for diploceline]. 

Symptoms Tree bark shrinks and cracks, often in concentric rings with the central piece of bark falling away. Deep lesions develop on the branches. Swelling can occur around the canker, and young twigs may die back. Cream-colored pustules may be seen in summer red spots are more common in fall. Papery bark can result Canker can ring an entire stem. Fruit skins crack fruits dry and can remain, mummified, on the tree. 

Three prenylated flavanones (144-146) isolated from stem barks of Erythrina abyssinica (family Liguminosae) exhibited inhibitory activity against protein tyrosine phosphatase IB (PTPIB) in an dose-dependent manner with IC50 values of > 60, 18.9 1.9 and 15.7 0.4 /tM, respectively hence, the flavanone (143) bearing a 2,2-dimethylpyran moiety on B ring is less potent than the other two (144 and 145) in the series. The... 

---