Advanced Chemophenetic Analysis of Essential Oil from Leaves of Piper gaudichaudianum Kunth (Piperaceae) Using a New Reduction-Oxidation Index to Explore Seasonal and Circadian Rhythms

Abstract

The aromatic species Piper gaudichaudianum Kunth (Piperaceae) is widely used in Brazil for medicinal and ritualistic applications. In the current study, chemophenetic patterns were realized across season and circadian rhythm based on the chemical profile of essential oils (EOs) from leaves. Hydrodistilled essential oils were analyzed by GC-MS and GC-FID, and a new calculation of metabolite oxidation level, averaged for each individual molecule component of the EO, was used to explore the patterns of metabolism/biosynthesis. This new index used an intermediate calculation, the ‘weighted average redox standard’ (SRO), to enable a value for mixtures of metabolites to be generated, the ‘general mixture redox index’ (GMOR). The indices were subjected to a proof-of-concept approach by making comparison to outcomes from multivariate analyses, i.e., PCA and HCA. Chemical analysis demonstrated that the essential oils were dominated by sesquiterpenes, constructed of 15 classes of compound (C-skeletons), and 4 C-skeletons were recognized in the monoterpene group, giving a total of 19. The variation of chemical profiles was distinct at different phenological stages, but stronger chemical variation was evident between day and night as compared to season. Furthermore, due to comprehensive sampling across different regions, nine chemotypes were recognized, including those previously reported. The SRO and GMRO indices demonstrate that phenological variation of chemistry is mainly an outcome of redox fluctuations in terpene biosynthesis, changing from day to night. These indices also corroborate that chemical diversity is increased with oxidative metabolism. Lastly, the current study demonstrates pronounced phenotypic plasticity in P. gaudichaudianum, which makes it a suitable candidate to help further our understanding of chemophenetics and chemical ecology.

Phenoplasticity of Essential Oils from Two Species of Piper (Piperaceae): Comparing Wild Specimens and Bi-Generational Monoclonal Cultivars

“…A study managed by our group [21] showed nine chemotypes for P. gaudichaudianum (i.e., δ-cadinene, 1-epi-cubenol, longipinanol, viridiflorol, α-humulene, E-caryophyllene, germacrene B, dillapiole and bicyclogermacrene), confirming this pronounced phenotypic chemical plasticity. Furthermore, we showed that EOs from P. gaudichaudianum from Rio de Janeiro are normally the bicyclogermacrene chemotype.…”

“…The chemical data in Table 1 is evaluated using two 'indices', which is the Shannon index, and the recently developed oxy-reduction index (Ramos and Moreira Index: GM RO ) [21]. These evaluations demonstrated a trend in the context of clonal chemical heritability.…”

“…Regarding essential oils (EOs), those obtained from the leaves of P. gaudichaudianum have shown in vitro larvicidal, insecticidal anti-inflammatory and cytotoxic activities [21]. There is also evidence of moderate antibacterial activity of EOs produced from the leaves of P. mollicomum [16].…”

“…There is also evidence of moderate antibacterial activity of EOs produced from the leaves of P. mollicomum [16]. Previous chemical studies show that the EOs from leaves of P. mollicomum and P. gaudichaudianum are predominantly terpenoid with traces of arylpropanoids, however their chemical constitutions vary according to their collection site, season, and time of day [15,[21][22][23][24][25].…”

Purely Australian Essential Oils Past and Present: Chemical Diversity, Authenticity, Bioactivity, and Commercial Value

“…When volatiles are studied, they can either be in the form of an essential oil or as a solvent extract. Furthermore, chemophenetic studies can be enriched by acknowledging biosynthetic relatedness between components, or by using oxidation indices to add another layer of complexity to the analysis and tease out more relationships, particularly in the context of circadian rhythms [69].…”