Ellagitannin Oligomers from Eucalyptus camaldulensis Leaves and Their Role in the Detoxification of Aluminum

TL;DR

This paper identifies new ellagitannin compounds in Eucalyptus leaves that help detoxify aluminum, explaining the plant's resistance to this metal in acidic soils.

Contribution

The first isolation and characterization of ellagitannin oligomers from Eucalyptus camaldulensis leaves with Al detoxification properties.

Findings

Novel dimeric and trimeric ellagitannin oligomers eucarpanin D2 and eucamalin A were isolated from E. camaldulensis leaves.

The ellagitannins showed good aluminum detoxification properties similar to previously known compound 12.

These findings suggest ellagitannins play a critical role in the plant's resistance to aluminum in acidic soils.

Abstract

Eucalyptus camaldulensis of the Myrtaceae family shows high resistance to aluminum (Al) ions and contains various compounds such as steroids, terpenoids, saponins, flavonoids, glycosides, alkaloids, and tannins. Although the ellagitannin oenothein B (12) isolated from E. camaldulensis exhibits remarkable properties for Al detoxification, likely contributing to its Al resistance, other ellagitannin oligomers present in E. camaldulensis have not been investigated in detail. In this study, novel dimeric and trimeric ellagitannin oligomers eucarpanin D2 (1) and eucamalin A (2), together with known gallotannins (7, 8, and 10), monomeric ellagitannins (4–6, and 11), and dimeric ellagitannins (3, 9, and 12–14), were isolated from E. camaldulensis leaves. The structures of these novel compounds were elucidated based on their chemical and physicochemical properties, including the orientations of tergalloyl groups in compounds 1 and 2. Similar to compound 12, previously isolated from the roots of E. camaldulensis, the ellagitannins demonstrated good Al detoxification properties. Hence, these tannins may play a critical role in the high Al resistance of E. camaldulensis in acidic soils. This paper reports for the first time the isolation of ellagitannin oligomers from the leaves of E. camaldulensis.

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