Introduction
C19H22O6 is an empirical chemical formula that represents a class of organic compounds containing nineteen carbon atoms, twenty‑two hydrogen atoms, and six oxygen atoms. The formula can correspond to a wide range of structural isomers, including alkaloids, flavonoids, terpenoids, and esterified derivatives. Because the formula is not unique to a single named compound, the article focuses on the general characteristics, synthesis, analytical determination, natural occurrence, and potential applications of molecules that fit this stoichiometry. The discussion is organized into sections that describe the molecular characteristics, common structural motifs, physical and spectroscopic properties, biosynthetic origins, laboratory preparation, analytical methods, safety considerations, and related research areas.
Molecular Formula and Structural Isomers
General Formula Significance
The empirical formula C19H22O6 indicates a saturated carbon skeleton with 19 carbon atoms. The ratio of hydrogen to carbon (22/19 ≈ 1.16) suggests that many of the carbon atoms are part of ring systems or unsaturated bonds, because a fully saturated alkane with 19 carbons would contain 40 hydrogen atoms (C_nH_2n+2). The presence of six oxygen atoms introduces functional groups such as hydroxyls, carbonyls, ethers, and esters. The overall degree of unsaturation can be calculated using the index of hydrogen deficiency (IHD):
- IHD = (2C + 2 – H)/2 = (2×19 + 2 – 22)/2 = (40 – 22)/2 = 9.
- Thus, each molecule that satisfies C19H22O6 contains nine degrees of unsaturation, which can be distributed among rings, double bonds, or other unsaturated functionalities.
Typical Functional Group Arrangements
Based on the required unsaturation, many known natural products with this formula adopt one or more of the following structural motifs:
- Flavonoid skeletons featuring a chromanone core and an additional phenyl ring.
- Terpenoid frameworks, such as bicyclic or tricyclic systems derived from geranyl or farnesyl units.
- Polyhydroxylated cyclohexane or cyclohexenone rings esterified with carboxylic acids.
- Alkaloid structures where nitrogen is replaced by oxygen atoms, creating lactones or lactams.
Because oxygen atoms can appear as part of lactones, lactams, or carboxylate esters, many C19H22O6 molecules are esterified polyhydroxy acids or contain cyclic ether bridges.
Representative Isomers
Below are brief descriptions of some well‑studied isomers that satisfy the C19H22O6 formula. These examples illustrate the diversity of structures possible within this empirical composition.
- Quercetin 3‑acetyl‑4′‑O‑benzoate – A flavonol derivative with an acetyl group and a benzoate ester, providing both aromatic and aliphatic oxygen functionalities.
- Oleanolic acid 3‑O‑methyl ester – A pentacyclic triterpenoid in which a carboxyl group is methylated, preserving the ring system while adding an ester oxygen.
- Coumarin‑7‑acetic acid 4‑methyl ester – A benzopyrone derivative that combines a lactone ring with an acetate ester and a methyl side chain.
- Bis‑acetyl‑myricetin – A diacetylated flavonol that introduces two acetyl groups on a highly polyhydroxylated backbone.
Physical and Spectroscopic Properties
Melting and Boiling Points
The physical properties of C19H22O6 compounds vary widely depending on the degree of hydrogen bonding and crystallinity. Small, rigid molecules such as coumarin derivatives typically exhibit melting points between 150 °C and 200 °C. In contrast, highly polar flavonoid esters often have melting points above 250 °C and may decompose before boiling due to their complex conjugated systems.
Solubility Behavior
Solubility is largely governed by the balance between hydrophobic aromatic rings and hydrophilic hydroxyl or ester groups. Many C19H22O6 molecules are soluble in polar organic solvents such as methanol, ethanol, and acetone. They often display limited solubility in water unless deprotonated or modified with ionic groups. In aqueous media, the presence of multiple hydroxyl groups can promote hydrogen bonding, leading to higher solubility in buffer solutions at physiological pH.
Infrared Spectroscopy
Characteristic IR absorptions for C19H22O6 compounds include:
- Broad O–H stretching bands around 3200–3500 cm⁻¹, indicating free or hydrogen‑bonded hydroxyl groups.
- C=O stretching bands near 1700 cm⁻¹ for lactones, esters, or ketones.
- Alkene C=C stretches around 1600–1650 cm⁻¹ for aromatic or unsaturated rings.
- Out‑of‑plane bending vibrations below 700 cm⁻¹ for substituted benzene rings.
Nuclear Magnetic Resonance
Proton NMR spectra typically show aromatic multiplets between 6.5 ppm and 8.5 ppm, corresponding to phenolic protons. Aliphatic protons on side chains or saturated rings appear between 0.8 ppm and 3.5 ppm. Carbon‑13 NMR signals for carbonyl carbons are observed around 160–180 ppm, while aromatic carbons resonate between 110 ppm and 160 ppm. The chemical shifts of hydroxyl protons are often broad and may exchange with deuterated solvents.
Mass Spectrometry
Electrospray ionization (ESI) or matrix‑assisted laser desorption/ionization (MALDI) spectra of C19H22O6 compounds usually display a prominent protonated molecular ion [M+H]⁺ at m/z 330. Deprotonated ions [M−H]⁻ are common in negative ion mode, especially for acidic esters. Fragmentation patterns often involve loss of water (−18 Da), acetyl groups (−42 Da), or benzoate fragments (−122 Da), providing diagnostic information for structure elucidation.
Natural Occurrence and Biosynthesis
Plant Sources
Compounds with the C19H22O6 formula are frequently isolated from higher plants, particularly in the families Fabaceae, Rutaceae, and Lamiaceae. They are often present in the essential oils, leaf extracts, or fruit skins of medicinal and culinary species.
- Flavonoid esters are common in the peels of citrus fruits, where they contribute to the characteristic aroma and antioxidant properties.
- Triterpenoid lactones are abundant in the bark of certain tree species and serve as defense molecules against herbivores.
- Lactone‑containing alkaloids appear in the roots of several medicinal plants, where they exhibit pharmacological activities.
Microbial Production
Some microorganisms, including certain fungi and actinomycetes, can biosynthesize C19H22O6 compounds via polyketide or non‑ribosomal peptide pathways. These microbial products often possess complex cyclic structures with multiple oxygen functionalities. Biotechnological exploitation of microbial pathways has led to the production of novel esterified flavonoids and lactones with improved bioactivity.
Biosynthetic Pathways
The synthesis of C19H22O6 molecules generally proceeds through the following steps:
- Methylerythritol phosphate (MEP) pathway for terpenoid backbones, generating geranyl or farnesyl diphosphate intermediates.
- Shikimate pathway for aromatic rings, providing phenylalanine and tyrosine precursors that feed into flavonoid biosynthesis.
- 3 Polyketide synthase (PKS) activity, catalyzing successive condensation reactions that build the carbon skeleton and introduce oxygen functionalities.
- Oxidative tailoring enzymes such as cytochrome P450 monooxygenases that introduce hydroxyl groups, lactonization, or esterification.
Enzymes involved in these pathways often exhibit high regio- and stereoselectivity, resulting in highly specific isomers that meet the C19H22O6 empirical formula.
Synthesis and Preparation
Laboratory Synthesis
In a synthetic context, C19H22O6 compounds are frequently constructed through a combination of classical organic transformations:
- Protection and deprotection strategies to shield reactive hydroxyl groups during esterification or acylation steps.
- Esterification reactions employing acyl chlorides, anhydrides, or carboxylic acids activated by carbodiimides (e.g., DCC) or coupling agents.
- Lactone formation via intramolecular esterification, often facilitated by Lewis acids or thermal cyclization.
- Aromatic substitution reactions, such as Friedel–Crafts acylation or Suzuki cross‑coupling, to attach additional aryl groups.
using reagents like PCC or Swern oxidation to convert alcohols into carbonyls or carboxylic acids.
Typical reaction sequences might begin with a flavone scaffold, followed by selective esterification of hydroxyl groups with benzoic acid derivatives. The resulting esterified product would satisfy the empirical formula C19H22O6.
Scale‑Up Considerations
Large‑scale synthesis of C19H22O6 compounds must address several factors:
- Use of renewable starting materials, such as plant‑derived aromatic compounds, to reduce cost.
- Minimization of hazardous reagents; for example, using organocatalysts instead of heavy metal complexes.
- Optimization of purification steps, often employing crystallization or preparative HPLC to achieve high purity.
- Implementation of green chemistry principles, such as solvent recycling and energy‑efficient heating.
Biotechnological Production
Microbial fermentation offers an alternative route to produce C19H22O6 molecules. Genetic engineering of microbial hosts can upregulate polyketide synthase genes or introduce heterologous pathways for triterpenoid biosynthesis. Process parameters - including media composition, pH, temperature, and aeration - are tuned to maximize yield. Downstream extraction commonly involves solvent partitioning followed by chromatography.
Applications and Bioactivity
Pharmacological Properties
Many C19H22O6 molecules exhibit significant biological activity. The most extensively studied effects include:
- Anaesthetic and analgesic actions of certain lactone‑containing alkaloids, attributed to their interaction with GABA_A receptors.
- Antioxidant activity of flavonoid esters, which scavenge reactive oxygen species and reduce oxidative stress in cellular models.
- Antimicrobial effects of triterpenoid lactones against Gram‑positive bacteria and fungi, possibly due to membrane disruption.
- Anti‑inflammatory actions observed for esterified coumarins, mediated through inhibition of cyclooxygenase enzymes.
Industrial Uses
Beyond pharmaceutical applications, C19H22O6 compounds find use in various industrial sectors:
- Flavor and fragrance ingredients derived from citrus flavonoids, imparting citrus or floral notes to food and cosmetic products.
- Photoinitiators for polymerization processes, particularly in the dental resin field where coumarin derivatives act as photoactive agents.
- Corrosion inhibitors formulated from triterpenoid lactones, providing protective films on metal surfaces.
- Bioactive additives in animal feed to improve gut health and immune responses.
Research and Development
Current research trends involving C19H22O6 compounds focus on:
- Structure‑activity relationship (SAR) studies to identify key functional groups responsible for biological activity.
- Derivatization to improve solubility, stability, and bioavailability, such as forming salt or prodrug forms.
- Targeted delivery systems, including nano‑carriers or liposomal formulations, to enhance therapeutic efficacy.
- Biotechnological optimization of microbial production, including metabolic flux analysis and pathway balancing.
- Assessment of environmental fate and biodegradability, particularly for fragrance and cosmetic applications.
Analytical Determination
Chromatographic Techniques
High‑performance liquid chromatography (HPLC) with diode array detection (DAD) is the most common method for separating and quantifying C19H22O6 molecules in complex matrices. Reverse‑phase columns (C18) provide suitable resolution for polar and non‑polar isomers. Mobile phase gradients typically involve water or aqueous buffer (pH 2–7) mixed with acetonitrile or methanol. Sample injection volumes are adjusted to avoid detector saturation.
Gas chromatography (GC) can be used for volatile lactone or triterpenoid derivatives, with flame ionization detection (FID) or mass spectrometry (MS) for enhanced sensitivity.
Spectroscopic Methods
Ultraviolet‑visible (UV‑Vis) spectroscopy provides a rapid screening tool for phenolic compounds, with absorption maxima near 280 nm and 360 nm. Fluorescence spectroscopy is particularly useful for coumarin derivatives, as they exhibit strong fluorescence when excited at 360 nm.
Spectrophotometric Assays
Colorimetric assays, such as the Folin–Ciocalteu method, are employed to estimate total phenolic content of plant extracts containing C19H22O6 molecules. This assay involves the reduction of the phosphomolybdic‑phosphotungstic acid complex, resulting in a blue color measured at 760 nm.
Calibration and Quantification
Calibration curves are generated by injecting known concentrations of authentic standards and plotting peak area versus concentration. Linear ranges typically span from 0.1 mg L⁻¹ to 10 mg L⁻¹, depending on detector sensitivity and instrument settings. Limits of detection (LOD) and limits of quantification (LOQ) for HPLC-DAD are generally below 0.05 mg L⁻¹.
Mass Spectrometric Methods
Quantitative mass spectrometry (QMS) employs multiple reaction monitoring (MRM) on a triple‑quadrupole instrument to monitor specific ion transitions (e.g., [M+H]⁺ → [M+H−H₂O]⁺). This approach provides high selectivity, particularly useful in complex biological matrices where co‑eluting substances may interfere with UV detection.
Safety and Handling
Hazard Assessment
Although many C19H22O6 compounds are relatively non‑toxic, certain lactone‑containing alkaloids may cause CNS depression or respiratory distress at high doses. General precautions include:
- Working in a well‑ventilated fume hood to avoid inhalation of volatile vapors.
- Using personal protective equipment (PPE) such as gloves, lab coat, and eye protection.
- Storing compounds at recommended temperatures, typically between 2 °C and 8 °C, to prevent degradation.
- Disposing of waste solvents and byproducts in accordance with institutional and governmental regulations.
Stability
Stability studies show that many C19H22O6 molecules are sensitive to light, heat, and pH changes. For example, esterified flavonoids can undergo hydrolysis under alkaline conditions, while lactones may open in the presence of strong acids. Photostability is particularly important for fragrance and cosmetic products; UV‑vis spectroscopy can monitor the degradation of coumarin derivatives over time.
References and Further Reading
While this review does not provide specific literature citations, key reference types for detailed study include:
- Primary research articles describing isolation and characterization of plant‑derived C19H22O6 compounds.
- Review papers on flavonoid and triterpenoid biosynthesis and bioactivity.
- Methodological papers on chromatographic and spectrometric analysis of esterified phenolics.
- Patent literature covering synthetic routes, derivatives, and pharmaceutical formulations.
- Textbooks on natural product chemistry, green synthesis, and biotechnological production methods.
Researchers are encouraged to consult these resources for in‑depth experimental details and the latest developments in the field.
Conclusion
Compounds with the empirical formula C19H22O6 represent a diverse group of organic molecules, spanning flavonoid esters, triterpenoid lactones, and lactone‑containing alkaloids. Their multifaceted chemical characteristics, rich natural occurrence, and valuable bioactivities make them important targets in pharmacology, flavor chemistry, and industrial applications. Continued exploration of biosynthetic pathways, synthetic optimization, and structure‑activity relationships will expand the utility of these compounds in both science and industry.
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