Isolation of gibberellins A26 and A 27 and their glucosides from immature seeds of Pharbitis nil

Advancing Glucose Conjugated Gibberellins Discovery: A Structure-Oriented Screening and Identification Method for Unraveling Gibberellin Metabolites in Plants

Gibberellins (GAs) play a pivotal role in modulating plant growth and development. Glucose-conjugated gibberellins (Glc-GAs), a prevalent conjugated form of GAs, regulate intracellular GA levels by the coupling and decoupling of glucose groups. However, the diversity of Glc-GAs identified within individual species remains limited, hinting at a multitude of yet undiscovered gibberellin metabolites. This lacuna poses considerable impediments to research efforts dedicated to comprehensively delineating the GA metabolic pathway. In this study, we developed a structure-oriented screening and identification method for Glc-GAs in plant species by employing LC-MS/MS coupled with chemical derivatization. Through the application of chemical derivatization technique, carboxyl groups on Glc-GAs were labeled which effectively enhanced the sensitivity and selectivity of mass spectrometry detection for these compounds. Concurrently, the integration of mass spectrometry fragmentation and chromatographic retention behavior facilitated the efficient screening and identification of potential Glc-GAs. With this strategy, we screened and identified 12 potential Glc-GAs from six plant species. These findings expand the Glc-GA diversity in plants and contribute to understanding GA metabolic pathways.

Identification and Evaluation of Apoptosis-Inducing Activity of Ipomone from Ipomoea nil: A Novel, Unusual Bicyclo-[3.2.1] Octanone Containing Gibberic Acid Diterpenoid

Ipomone (1), a novel diterpenoid along with seven known compounds (2-8), was isolated for the first time from the acidified hydroalcoholic extract of Ipomoea nil seeds. The structures of the isolated compounds were elucidated via comprehensive NMR spectroscopic data. The absolute configuration of 1 was ascertained through NOESY, NMR, and ECD analyses. Compound 1 was found to contain an unusual bicyclo-[3.2.1] octanone, which appeared first time in any natural product that might be an artifact resulting from the acid-catalyzed 1,2 alkyl shift/rearrangement. The novel compound was screened for cytotoxic activity against a panel of 12 human cancer cell lines and exhibited weak cytotoxicity with IC₅₀ values in the range of 34-86 μM (except for HEK-293 cells). Microscopic studies revealed that compound 1 induced apoptosis and autophagy in A549 cells. To further explore the signaling pathway involved, immunoblot analysis was performed that confirmed inhibition of apoptotic proteins PARP-1 and caspase-3 expression and upregulation of LC3B expression by compound 1. The compound was further subjected to molecular docking studies to evaluate its binding affinity with p110α, PARP-1, and caspase-3 proteins.

Biological activity of some conjugated gibberellins

The biological activity of several gibberellin (GA) conjugates was studied and compared with that of the corresponding free GAs. The following conjugates were included: O(3)-β-D-glucopyranosides of GA1, GA3 and GA4; O(13)-β-D-glucopyranosides of GA1, GA3 and GA5; O(13)-β-D-glucopyranosyl-GA5-β-D-glucopyranosyl ester; GA3-β-D-glucopyranosyl ester and GA3-α-D-glucopyranosyl ester; N-GA3-oyl-glycine, its methyl ester, N-GA3-oyl-glycylglycine, and N-GA3-oyl-proline. All compounds were synthesized chemically but some of them are known to occur as endogenous plant products, or to be formed in plants upon application of a free GA. Activity was determined in the dwarf pea, dwarf corn, dwarf rice, and lettuce hypocotyl bioassays. The GA conjugates were found to posses different relative activities depending on the chemical structure, the bioassay system, and the site of application (shoot or roots). It is concluded that the activity of GA conjugates as measured in different bioassays is based upon the ability of plant enzymes and possibly of certain microorganisms to hydrolyze glucosidic, glucosyl ester, and amide-like linkages.

Formation of bound gibberellins inPharbitis nil

Developing seeds ofPharbitis nil accumulate free as well as bound gibberellins until a maximum level is reached at approximately 25 days after anthesis. Seeds from CCC-treated parent plants have a strongly reduced level of free as well as bound gibberellins. When different spray reagents were used it was found that trichloroacetic acid in particular was suitable to locate non-hydrolysed bound GA fractions on thin-layer plates. Chromatography showed two major bound GA fractions, determined with spray reagents as well as by means of hydrolysis.(3)H-GA1 applied to youngPharbitis plants was converted to two water-soluble compounds present in the aqueous phase. The rate of conversion was significantly enhanced when(3)H-GA1 and(14)C-glucose were applied to the same plants. Chromatography indicated that one of the conversion products of(3)H-GA1 became at least partly associated with the applied(14)C-glucose (or its products). This suggestion was also supported by the fact that mild acid hydrolysis of the aqueous fraction resulted in the reappearance of(3)H-GA1 and a conversion product of(3)H-GA1, including a(14)C-radioactivity peak cochromatographing with(14)C-glucose. However, the conversion products obtained with(3)H-GA1 applied to plants appeared to be chromatographycally different from any of the bound-GA fraction established by means of hydrolysis or spray reagents in developing seeds.

The red light controlled production of gibberellin in etiolated wheat leaves

Most of the gibberellin activity detectable in extracts of etiolated wheat leaf tissue occurs in a bound form. There is a rapid increase in extractable gibberellin-like substances following exposure of the tissue to red light with a concomitant fall in the amount of bound gibberellin. Actinomycin-D and AMo 1618 do not inhibit this initial phase of red light stimulated gibberellin production.It is concluded that red light stimulated gibberellin production in etiolated wheat leaf tissue is due to release from a bound form and to synthesis.

Isolation of gibberellin A8-glucoside from shoot apices of Althaea rosea

Gibberellin A8-glucoside has been isolated from shoot apices of Althaea rosea. It showed a weak growth-promoting activity on rice seedlings and oat mesocotyl sections but did not induce germination of lettuce seeds in darkness.