Occurrence and Distribution of Phytochemicals in the Leaves of 17 In vitro Cultured Hypericum spp. Adapted to Outdoor Conditions

Abstract

A plethora of plants belonging to the genus Hypericum have been investigated so far owing to the biological efficacies of pharmacologically important secondary metabolites produced by several Hypericum species. However, there is currently a dearth of information about the localization (accumulation) of these compounds in the plants in situ. In particular, the biosynthetic and ecological consequence of acclimatization of in vitro cultured Hypericum spp. to outdoor conditions is not fully known. Herein, we report an application of matrix-assisted laser desorption/ionization high-resolution mass spectrometry (MALDI-HRMS) to reveal the distribution of major naphthodianthrones hypericin, pseudohypericin, protohypericin, and their proposed precursor emodin as well as emodin anthrone, along with the phloroglucinol derivative hyperforin, the flavonoids quercetin, quercitrin, rutin and hyperoside (and/or isoquercitrin), and chlorogenic acid in Hypericum leaves. Plants encompassing seventeen Hypericum species classified into eleven sections, which were first cultured in vitro and later acclimatized to outdoor conditions, were studied. We focused both on the secretory (dark and translucent glands, other types of glands, and glandular-like structures) as well as the non-secretory leaf tissues. We comparatively analyzed and interpreted the occurrence and accumulation of our target compounds in different leaf tissues of the seventeen species to get an intra-sectional as well as inter-sectional perspective. The naphthodianthrones, along with emodin, were present in all species containing the dark glands. In selected species, hypericin and pseudohypericin accumulated not only in the dark glands, but also in translucent glands and non-secretory leaf tissues. Although hyperforin was localized mainly in translucent glands, it was present sporadically in the dark glands in selected species. The flavonoids quercetin, quercitrin, and hyperoside (and/or isoquercitrin) were distributed throughout the leaves. Rutin was present only within sections Hypericum, Adenosepalum, Ascyreia, and Psorophytum. Our study provides insights into the prospects and challenges of using in vitro cultured Hypericum plants, further adapted to field conditions, for commercial purposes.

Chemometric evaluation of hypericin and related phytochemicals in 17 in vitro cultured Hypericum species, hairy root cultures and hairy root-derived transgenic plants

“…Interestingly, a high content of pseudohypericin was detected in H. tomentosum in the present study, even though this species is characterized by the presence of only one or two dark glands on the leaf apex. This further upholds our earlier studies, [17,34] wherein pseudohypericin was also found to be localized in the dark glands located on the apex of H. tomentosum leaves. Our evaluation of the presence of hypericins further agrees with the previously published study by Ko suth et al (2011), [23] who studied the content of hypericin, pseudohypericin and emodin in in vitro grown seed-derived plants of 15 species of the genus Hypericum using HPLC-tandem mass spectrometry.…”

“…It was noted that the flavonoid rutin was not present in 7 Hypericum species, namely H. tetrapterum , H. rumeliacum , H. humifusum , H. tomentosum , H. pulchrum , H. androsaemum and H. kalmianum . The Hypericum species belonging to the section Ascyreia (i.e. H. stellatum , H. monogynum and H. kouytchense ), H. balearicum , H. perforatum , H. annulatum and H. bupleuroides contained rutin in all plant organs.…”

“…Several other studies unravelling the phytochemical compositions of different Hypericum species have been reported . More recently, we performed extensive MALDI‐HRMS analyses to investigate in detail the spatial distribution of the major compounds in the leaves of 17 of Hypericum species classified into 11 sections, which were first cultured in vitro and later acclimatized to outdoor conditions …”

“…[7,[13][14][15][16] More recently, we performed extensive MALDI-HRMS analyses to investigate in detail the spatial distribution of the major compounds in the leaves of 17 of Hypericum species classified into 11 sections, which were first cultured in vitro and later acclimatized to outdoor conditions. [17] Genetic transformation of plants offers an opportunity to introduce new functional traits into medicinal plant species. For many plant species, hairy roots are not only able to synthesize comparable or higher levels of secondary metabolites concomitant to those of intact plant roots, but also can be used to discover novel metabolites.…”

Phenotyping the genus Hypericum by secondary metabolite profiling: emodin vs. skyrin, two possible key intermediates in hypericin biosynthesis

“…[7, 16]. In this paper, we tentatively identified new compounds present in the genus Hypericum and proposed that the anthraquinone skyrin is the key intermediate in hypericin biosynthesis.…”