Two benzophenone O-arabinosides and a chromone from Hypericum annulatum

Area of Science:

• Phytochemistry
• Natural Product Chemistry
• Organic Chemistry

Background:

• Hypericum species are known sources of diverse bioactive compounds.
• Benzophenone glycosides and chromones are classes of natural products with potential pharmacological activities.
• The chemical investigation of Hypericum annulatum is crucial for discovering novel compounds.

Purpose of the Study:

• To isolate and characterize chemical constituents from Hypericum annulatum.
• To identify new benzophenone O-arabinosides and other secondary metabolites.
• To investigate the co-occurrence of specific phytochemicals within the plant.

Main Methods:

• Methanol and chloroform extraction of Hypericum annulatum herb.
• Isolation of compounds using chromatographic techniques.
• Structure elucidation of isolated compounds via spectral (NMR, MS) and chemical methods.

Main Results:

• Two novel benzophenone O-arabinosides, annulatophenonoside (1) and acetylannulatophenonoside (2), were isolated and structurally characterized.
• Compound 1: 2-O-alpha-L-arabinofuranosyl-3",5",6-trihydroxy-4-methoxybenzophenone.
• Compound 2: 2-O-alpha-L-3"-acetylarabinofuranosyl-3",5",6-trihydroxy-4-methoxybenzophenone.
• A known chromone, 5,7-dihydroxy-3-methylchromone (3), was isolated from the chloroform extract, representing its first isolation from a natural source.
• The co-occurrence of these compounds with 1,5,7-trihydroxy-3-methoxyxanthone was not observed.

Conclusions:

• The study successfully identified two new benzophenone O-arabinosides from Hypericum annulatum.
• The isolation of 5,7-dihydroxy-3-methylchromone from a plant source is a significant finding.
• The absence of xanthone co-occurrence provides insights into the plant's biosynthetic pathways or ecological interactions.