Diversity of secoiridoid glycosides in leaves of UK and Danish ash provide new insight for ash dieback management

Abstract

Secoiridoid glycosides are anti-feeding deterrents of the Oleaceae family recently highlighted as potential biomarkers in Danish ash trees to differentiate between those tolerant and susceptible to the fungal disease ash dieback. With the knowledge that emerald ash borer has recently entered Europe from Russia, and that extensive selection trials are ongoing in Europe for ash dieback tolerant European ash (Fraxinus excelsior), we undertook comprehensive screening of secoiridoid glycosides in leaf extracts of trees tolerant and susceptible to ash dieback sampled from sites in the UK and Denmark. Here we report an unexpected diversity of secoiridoid glycosides in UK trees and higher levels of secoiridoid glycosides in the UK sample group. While it is unlikely that secoiridoid glycosides generally can serve as reliable markers for ash dieback susceptibility, there are differences between tolerant and susceptible groups for specific secoiridoids. We predict that the high levels—and structural diversity—of secoiridoids present in the UK group may provide a robust reservoir of anti-feeding deterrents to mitigate future herbivore threats such as the Emerald ash borer.

Neuroprotective effects of oleuropein: Recent developments and contemporary research

“…There is no set recommended dosage for oleuropein intake per day but many studies have shown that olive leaf extract (containing approximately 20% oleuropein) at the dose of 1,000 mg/day depicted no observed adverse side effects (Breakspear & Guillaume, 2020; Clewell et al., 2016). OL is not solely a component of Olea genus, it also occurs in several other genera of Oleaceae family such as Fraxinus chinensis (Chang et al., 2020), F. angustifolia (Kasmi et al., 2021), F. excelsior (Sidda et al., 2020), Syringa vulgaris (Hanganu et al., 2021), S. josikaea (Damtoft et al., 1993), Ligustrum vulgare (Macková et al., 2013), L. ovalifolium (Hosny et al., 2009), and Philyrea latifolia (Tattini et al., 2000). Table 1 represents the oleuropein content in different parts/products of olive tree.…”

Profiles of secoiridoids and alkaloids in tissue of susceptible and resistant green ash progeny reveal patterns of induced responses to emerald ash borer in Fraxinus pennsylvanica

“…2781 ) and GL5 ( m/z 928 . 3429 ), found in higher concentrations in trees that are highly susceptible to ash dieback in previous investigations (39, 49), were significantly higher in low larval kill individuals compared to uninfested individuals across families. Additionally, we found that concentrations of verbascoside, a phenylethanoid glycoside also proposed as a component of the resistance response (36), were highest in low larval kill individuals.…”

“…One secoiridoid (m/z 569.23) was elevated in all infested comparisons (LLK v UNI, HLK v UNI) across all families, and may have some value as an indicator of infestation across many ash genotypes. Another two secoiridoids, nueznehide (m/z 704.2781) and GL5 (m/z 928.3429), found in higher concentrations in trees that are highly susceptible to ash dieback in previous investigations (39,49), were significantly higher in low larval kill individuals compared to uninfested individuals across families. Additionally, we found that concentrations of verbascoside, a phenylethanoid glycoside also proposed as a component of the resistance response (36), were highest in low larval kill individuals.…”

“…This association is consistent with previous studies that suggested that infested trees, or trees artificially stressed with methyl jasmonate produced higher amounts of these metabolites (52). High concentrations of specific secoiridoids in F. excelsior are proposed to be indicative of tolerance (40) or susceptibility to ash dieback (37), and were predicted to provide a future robust reservoir of anti-feeding deterrents to EAB (49). Our data suggests that these specific secoiridoids function best as indicators of a generalized stress response and not necessarily of resistance to EAB.…”

Solid State Fermentation of Olive Leaves as a Promising Technology to Obtain Hydroxytyrosol and Elenolic Acid Derivatives Enriched Extracts

“…Finally, compounds 81 with m/z 601 and molecular formula C 27 H 38 O 15 was tentatively identified as frameroside or 2″-epi-frameroside; Sidda and co-workers [ 39 ] identified them in ash leaves from Oleaceae family.…”