K.K. Talwar

Structure and plant growth activity relationship in terpenoid lactones

Abstract In order to obtain structure—biological activity data the synthesis of 15 new terpenoid lactones from germacranolides, eudesmanolides, guaianolides and elemanolides was undertaken. These and 15 other compounds were then tested as plant growth regulators. These studies established that the biological activity associated with the α-methylene-γ-lactone moiety in a terpenoid lactone is further enhanced when a cyclopropane ring is placed in the α,β-position to the lactone carbonyl. No exception to this structure—activity data has been noted so far. Significantly, this activity is increased when a trisubstituted (Z)-double bond is in the position of conjugation and the only exception to this is (Z)-C13-methyl dehydrosaussurea lactone which is only as active as water. Almost always a C-4 epoxy, or a C-4, C-10 ether group in the guaianolide systems further enhances the biological activity associated with the parent lactone. A similar effect of the epoxy group is not observed in the case of eudesmanolides.

A sesquiterpenoid with plant growth regulatory activity fromSaussurea lappa

Abstract Saussureal, a sesquiterpenoid with a new type of modified eudesmane skeleton has been isolated from roots of Saussurea lappa . In saussureal, ring A is five-membered and displays significant biological activity as a plant growth regulator. Its structure has been elucidated on the basis of spectral data and chemical correlation with α-santenolide.

Stereostructures of two biologically active sesquiterpene lactones from Inula racemosa

Abstract Two new sesquiterpene lactones, alantodiene and isoalantodiene, have been isolated from Inula racemosa . Both lactones display biological activity as plant growth regulators. Their structures have been elucidated using spectral data and chemical correlation. The most active plant growth regulator yet isolated from this source is isoalantodiene which is a potent root initiator with hypocotyl cuttings of Vigna radiata and it also increases the nitrate reductase activity in this plant.

Dehydrocostuslactone and plant growth activity of derived guaianolides

Abstract The stereostructures of two new guaianolides, isodehydrocostuslactone and isozaluzanin C, isolated previously from Saussurea lappa, have been confirmed by their correlation with dehydrocostuslactone. Twenty new derivatives have been synthesized from these guaianolides and these have been tested as plant growth regulators. The conjugated lactones which have an exocyclic methylene group at C-4 conjugated with a C-3 ketone, show distinct enhancement in their root-forming potential, as compared with their 3-deoxy derivatives. Of further significance is the fact that these ketones display maximum activity only at lower concentrations. Other compounds show the expected structure-biological activity relationships displayed in general by guaianolides. However, the presence of an epoxide at the C-3, C-4 position does not affect the biological activity, which is indeed the case when the epoxide group occupies the C-4, C-14 position in guaianolides. The major biological parameter studied was rooting in-stem cuttings of Phaseolus aureus.

A biologically active guaianolide from Saussurea lappa

Abstract 4β-Methoxydehydrocostus lactone has been isolated from costus roots ( Saussurea lappa ). Its structure and stereochemistry have been established by spectral methods and chemical correlation with dehydrocostus lactone. The compound displayed significant biological activity as a plant growth regulator.

A dramatic effect of stereochemistry on the plant growth activity of the cadinane group of terpenoids

Abstract Seven cadinane terpenoids have been tested as plant growth regulators. Khusinoloxide and epikhusinol acetate greatly stimulated root initiation with hypocotyl cuttings of Phaseolus aureus seedlings.

Epoxy alantolides: Isoinunal—a new potent plant growth regulator from Inula racemosa

Abstract An investigation of Inula racemosa roots afforded, in addition to known sesquiterpene lactones, four new lactones with close biogenetic relationships. Their structures have been elucidated using spectral data and chemical correlation. The most interesting of these is isoinunal which is a potent root initiator with hypocotyl cuttings of Phaseolus aureus .

Plant growth activity of guaianolides with C-4 oxygen-containing groups

Abstract The plant growth activity of guaianolides with C-4 oxygen-containing functions has been studied. It was found that the presence of an epoxy or an ether link at C-4 enhanced the plant growth activity of the parent compound. The presence of a hydroxyl group at C-4 had no effect.

A facile E,Z-isomerization of α,β-unsaturated terpenoid lactones and its effect on plant growth activity

Abstract Various synthetic C-16 lactones prepared in earlier work are the Z -isomers. These have been isomerized chemically to the corresponding E -isomers. It is observed that these isomers have different root initiating properties, which reflect the significance of the geometry of double bonds in conjugated γ-lactones which act as plant growth regulators.

Dihydroparthenin, a pseudoguaianolide from tissue culture of Parthenium hysterophorus

Abstract From the callus of P. hysterophorus a new pseudoguaianolide, dihydroparthenin has been isolated. Other known pseudoguaianolides have also been detected in the callus by HPLC.