3-Hydroxy-4-Methoxybenzoic Acid - an overview (2023)

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Bioaccesibility and bioavailability of marine polyphenols

Salud Cáceres-JiménezJosé Luis Ordóñez-DíazJosé Manuel Moreno-RojasGema Pereira-Caro, in Marine Phenolic Compounds, 2023

2 Algae marine polyphenols: Source and their occurrence

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Source: microalgae and macroalgae (seaweed)

There are more than 11,000 different species of algae divided into two groups: microalgae and macroalgae or seaweed (Jimenez-Lopez et al., 2021).

-: Microalgae are a highly diverse group of unicellular eukaryotic organisms (Mateos et al., 2020) that have been proposed as an alternative source of natural antioxidants due to their metabolic diversity and adaptive flexibility compared to higher plants (Li et al., 2007; Safafar et al., 2015). However, the phenolic compounds present in microalgae tend to be less studied than those in terrestrial plants (Sansone and Brunet, 2019). Simple phenolic acids such as hydroxybenzoic and hydroxycinnamic acids have been reported to be the major families identified in microalgae (Mateos et al., 2020). These phenolic acids include 3,4-dihydroxybenozic acid, chlorogenic, 3′,4′-dihydroxycinnamic acid, 3,4,5-trihydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid, and 4′-hydroxy-3′-methoxycinnamic acid, among others (Jerez-Martel et al., 2017; Scaglioni et al., 2019).
-: Macroalgae, also known as seaweed, are grouped into three classes according to their pigment content: red seaweeds (Rhodophyceae), green seaweeds (Chlorophyceae), and brown seaweeds (Phaeophyceae) (Tanna and Mishra, 2018). Within these classes of macroalgae, brown algae are those with the highest content of phenolic compounds (Heffernan et al., 2015; Montero et al., 2017). The total polyphenolic content of brown seaweed is around 12%–14% of its dry mass, the content in red and green algae being much lower (maximum 5% of dry mass) (Holdt and Kraan, 2011; Shannon et al., 2021). In fact, brown algae are the most studied in terms of the bioavailability of phenolic compounds, possibly due to the presence of phlorotannins. Indeed, there is a family of brown algae called Fucaceae, which is the most dominant algae family along Northern Hemisphere shorelines (Catarino et al., 2017).

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Polyphenols: Simple phenolics, bromophenols, and phlorotannins

-: Simple phenolics. They are mainly made up of two phenolic groups, hydroxycinnamic acids and hydroxybenzoic acids. The presence of these compounds has mainly been reported in brown algae (Mateos et al., 2020). Among hydroxycinnamic acids, it is worth highlighting 4′-hydroxycinnamic acid (I), 3′,4′-dihydroxycinnamic acid (II), 4′-hydroxy-3′-methoxycinnamic acid (III), chlorogenic acid (IV), and sinapic acid (V) (Jimenez-Lopez et al., 2021). On the other hand, hydroxybenzoic acids include 3,4,5-trihydroxybenzoic acid (VI), p-hydroxybenzoic acid (VII), 4-hydroxy-3-methoxybenzoic acid (VIII), and 3,5-dimethoxy-4-hydroxybenzoic acid (IX), among others (Jimenez-Lopez et al., 2021) (Fig. 1, Structures I-IX).
Fig. 1. Chemical structures of the main marine polyphenols: simple phenolics, bromophenols, and phlorotannins.
See Also
Chemical constituents from the stems and leaves of Glycosmis craibii var. glabra (Craib) Tanaka and their chemotaxonomic significance Lignin Chemistry And Applications Ebook PDF Applications of Claisen condensations in total synthesis of natural products. An old reaction, a new perspective Accumulation of podophyllotoxin and related lignans in cell suspension cultures of linum album
-: Bromophenols. They are secondary metabolites found in red, green, and brown seaweed (Mateos et al., 2020), where the red variety is the major natural source of these bioactives (Cotas et al., 2020; Liu et al., 2011). They are composed of one to five phenol groups with varying degrees of bromination (Cotas et al., 2020; Shannon et al., 2021). Specifically, tri-bromophenols are the most common metabolites found in seaweeds, followed by di- and mono-bromophenols (Chung et al., 2003; Shannon et al., 2021). Examples of these bromophenol groups are shown in Fig. 1 (Structures X, XI, and XII). Compared to phlorotannins, bromophenols are present in limited amounts in algae, so fewer studies have been conducted on their isolation and characterization (Cotas et al., 2020), despite red algae being the subject of extensive research.
-: Phlorotannins. Compared with other polyphenols produced by seaweeds, phlorotannins are the most studied group. They are found in brown seaweeds (Francisco et al., 2020), Eisenia, Ecklonia, and Ishige genera being the main sources of bioactives (Erpel et al., 2020; Rosa et al., 2020). These secondary metabolites are characterized by a unique structure that is not found in terrestrial plants (Cotas et al., 2020; Freile-Pelegrín and Robledo, 2013). They are composed of phloroglucinol units (1,3,5-trihydroxybenzene) and four groups of phlorotannins exist depending on the linkages between these phloroglucinol units, which are fuhalols (XIII) and phlorethols (XIV) (with ether linkages), fucols (XV) (with phenyl linkages), fucophlorethols (XVII) (with phenyl and ether linkages), and eckols (XVI) (with dibenzodioxin linkages) (Rosa et al., 2020; Singh and Sidana, 2013). Examples of these phlorotannins groups are shown in Fig. 1 (Structures XIII-XVII). Consequently, phlorotannins constitute a very heterogeneous group of compounds, which present a wide range of molecular sizes (126Da to 650 KDa), commonly found in the 10–100kDa range (Freile-Pelegrín and Robledo, 2013; Steevensz et al., 2012). It is believed that the activity of these compounds depends on their molecular weight; the greater the degree of polymerization, the greater its activity (Kirke et al., 2019; Meng et al., 2021). Compared with phenolic compounds from terrestrial plants, phlorotannins from brown seaweeds have better antioxidant activity (Balboa et al., 2013; Meng et al., 2021). Several in vitro and in vivo in animal studies have analyzed their bioactivity, showing their potential pharmacological and food applications. However, metabolomic studies and clinical trials focusing on the biological response of phlorotannins in the body are scarce (Erpel et al., 2020; Meng et al., 2021).

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Actinide Chemistry

G. Geipel, in Coordination Chemistry Reviews, 2006

As the treatment of fluorescence spectra containing emissions from excited state reactions for the evaluation of complex formation reactions has not been completely solved until now, this method was applied to a ligand that does not show such a reaction under the experimental conditions selected. At pH values above 5.0, 4-hydroxy-3-methoxybenzoic acid (vanillic acid) does not undergo excited state reactions. As evidence for the absence of excited state reactions the Stokes shift between the absorption and the corresponding fluorescence maximum should be about 5000cm⁻¹ [32]. Stokes shifts of about 4500cm⁻¹ were determined for both the monovalent and the divalent anion of 4-hydroxy-3-methoxybenzoic acid. Nevertheless in this work [33] the correction of inner filter effects [34], which may be caused by absorption of the incident laser beam and by absorption of emitted fluorescence signal by the sample itself, must be applied.

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Chemical composition, health benefits and future prospects of Paulownia flowers: A review

Na Guo, ... Guo-Qiang Fan, in Food Chemistry, 2023

4.2.6 Others

Currently, only two lignans have been reported in Paulownia flowers, paulownin (Meng et al., 2014), and pinoresinol (Jin et al., 2015). Catalpol, a primary iridoid, has been detected in the flowers of P. Clon (Stochmal et al., 2022). Also, phenolic acids, namely, 4-hydroxy-3-methoxybenzoic acid, vanillic acid, and p-hydroxybenzoic acid, have been separated from Paulownia flowers (Feng, 2018). In addition, arbutin, nicotinic acid, thymidine, thymine, 4-hydroxybenzyl-beta-d-glucoside, p-ethoxybenzaldehyde, 1-acetoxy-3-hydroxypropan-2-yl-3-hydroxypentanoate, and dehydrovomifoliol were also isolated from these flowers (Feng, 2018; Jin et al., 2015; Li et al., 2009; Yuan et al., 2009).

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Biologically active compounds and pharmacological activities of species of the genus Crocus: A review

Olga Mykhailenko, ... Victoriya Georgiyants, in Phytochemistry, 2019

3.4.2 Tepals and petals

Hydroxybenzoic acids are the precursors in the flavonoid biosynthesis and are often found in Crocus species. Li et al. (2004) isolated and identified several hydroxycinnamic acids from C. sativus petals, namely р-coumaric acid 107, protocatechuic acid 111, protocatechuic acid methyl ester 120, methylparaben 121, vanillic acid 112, p-hydroxybenzoic acid 113, 3-hydroxy-4-methoxybenzoic acid 114 and a new naturally occurring acid, (3S),4-dihydroxybutyric acid 119 (Fig. 9). Using LC-DAD-MS (ESI+) and LC-ESI-IT/MS methods, in C. sativus petals sinapic acid 108 (Termentzi and Kokkalou, 2008) and sinapic acid derivative (Monotro et al., 2012) were identified. Catechin hydrate, caffeic acid 104 and ferulic acid 106 were identified in C. cancellatus subsp. Damascenus stigmas (Loizzo et al., 2016).

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New wedelolides, (9R)-eudesman-9,12-olide δ-lactones, from Wedelia trilobata

Toan Phan Duc, ... Quang Ton That, in Phytochemistry Letters, 2016

3.4 Extraction and isolation

The crude EtOH residue of dried leaf powder of W. trilobata (1.8kg), was successively extracted with hexane and CH₂Cl₂. The CH₂Cl₂ extract was subjected to silica gel column chromatography (CC) eluted with hexane/CHCl₃ (9.5:0.5 to 0:10, v/v, 4L), followed by CHCl₃/MeOH (9.5:0.5 to 2:8, v/v, 4L), affording sixteen fractions (1⿿16). Bioactive fraction 6 (12.6g), obtained from the elution of CHCl₃/MeOH of 9.5:0.5, was further purified by preparative TLC (CH₂Cl₂/MeOH, 9:1) followed by RP-C18 HPLC eluted with CH₃CN/H₂O (65:35), to afford new compounds, wedelolide G (1) (10.0mg) and wedelolide H (2) (5.0mg), respectively. Fraction 8 (16.43g), obtained from the elution of CHCl₃/MeOH of 9:1, was subjected to silica gel CC, eluted with hexane/AcOEt (from 9:1 to 5:5, v/v), to yield sub-fractions 8A⿿8K. Sub-fraction 8C was extensively chromatographed on columns of silica gel and Sephadex LH-20 (CHCl₃⿿MeOH, 6:4, 3.2ÿ140cm) to afford compounds 3 (7.6mg), 4 (12.8mg), and 5 (6.3mg). Sub-fraction 8E was submitted to a silica gel CC, eluted with increasing concentrations of AcOEt in petroleum ether (from 8:2 to 5:5, v/v), as well as preparative TLC eluted with hexane/acetone (9:1, v/v) yielding 6 (7.1mg), 7 (34.8mg), and 8 (9.1mg). The structures of these eight compounds (Fig. 1) are identified by spectroscopic methods and optical activity.

Wedelolide G (1) [(1S,4S,5S,6R,7S,8S,9R,10S)-1α,4β-dihydroxy-6α,8β-diisobutyryloxyeudesman-9,12-olide]: white, amorphous solid, [α]²⁰_D ⿿7 (c 0.1, MeOH); HR-ESI⿿MS m/z=461.2146 [M+Na]⁺ (calcd for C₂₃H₃₄O₈, 461.2151); ¹H NMR (CDCl₃) and ¹³C NMR (CDCl₃), see Table 1.

Wedelolide H (2) [(1S,4S,5S,6R,7S,8S,9R,10S)-1α,4β-dihydroxy-6α-isobutyryloxy-8β-methacryloxyeudesman-9,12-olide]: white, amorphous solid, [α]²⁰_D ⿿9 (c 0.1, MeOH); HR-ESI⿿MS m/z=459.1989 [M+Na]⁺ (calcd for C₂₃H₃₂O₈, 459.1995); ¹H NMR (CDCl₃) and ¹³C NMR (CDCl₃), see Table 1.

5-Hydroxymethylfurfuran (3): yellow, amorphous solid. ¹H NMR (CDCl₃): 9.55 (1H, s, H), 7.21 (1H, d, J=3.5Hz, H-3), 6.50 (1H, d, J=3.5Hz, H-4), 4.69 (2H, s). ¹³C NMR (CDCl₃): 152.4 (C-2), 123.0 (C-3), 110.1 (C-4), 160.9 (C-5), 57.6 (CH₂OH), 177.8 (CHO).

4-Hydroxy-3-methoxybenzoic acid (vanillic acid) (4): white, amorphous solid. ¹H NMR (DMSO-d₆): 7.44-7.42 (2H, m, H-2, H-6), 6.83 (1H, d, J=9.0Hz, H-5), 3.55 (3H, s, OCH₃). ¹³C NMR (DMSO-d₆): 167.4 (COOH), 150.9 (C-4), 147.1 (C-3), 123.4 (C-6), 122.0 (C-1), 115.0 (C-5), 112.8 (C-2), 55.5 (3-OCH₃).

5,4⿲-Dihydroxy-7-methoxyflavone (5): yellow, amorphous solid. ¹H NMR (DMSO-d₆): 12.97 (1H, brs, 5-OH), 7.97 (2H, d, 9.0Hz, H-2⿲,6⿲), 6.95 (2H, d, 9.0Hz, H-3⿲,5⿲), 6.86 (1H, s, H-3), 6.79 (1H, d, 2.0Hz, H-8), 6.39 (1H, d, 2.0Hz, H-6), 3.88 (3H, s, ⿿OCH₃). ¹³C NMR (DMSO-d₆): 56.0 (7-OCH₃), 164.1 (C-2), 103.0 (C-3), 181.9 (C-4), 161.3 (C-5), 97.9 (C-6), 165.1 (C-7), 92.7 (C-8), 157.4 (C-9), 104.6 (C-10), 121.0 (C-1⿲), 128.5 (C-2⿲,6⿲), 115.9 (C-3⿲,5⿲), 161.2 (C-4⿲).

5,3⿲,4⿲-Trihydroxy-7-methoxyflavone (6): yellow, amorphous solid. ¹H NMR (DMSO-d₆): 13.05 (1H, brs, 5-OH), 7.42 (1H, dd, 8.5, 2.0Hz, H-6⿲), 7.37 (1H, d, 2.0Hz, H-2⿲), 6.89 (1H, d, 8.5Hz, H-5⿲), 6.71 (1H, d, 2.0Hz, H-8), 6.33 (1H, d, 2.0Hz, H-6), 6.66 (1H, s, H-3), 3.98 (3H, s, ⿿OCH₃). ¹³C NMR (DMSO-d₆): 55.9 (7-OCH₃), 164.8 (C-2), 101.5 (C-3), 181.4 (C-4), 161.2 (C-5), 97.7 (C-6), 164.8 (C-7), 92.7 (C-8), 157.0 (C-9), 104.5 (C-10), 119.7 (C-1⿲), 111.6 (C-2⿲), 146.6 (C-3⿲), 154.0 (C-4⿲), 115.5 (C-5⿲), 119.7 (C-6⿲).

Methyl caffeate (7): white needles. ¹H NMR (DMSO-d₆): 7.48 (1H, d, J=15.5Hz, H-3), 7.05 (1H, d, J=2.0Hz, H-2⿲), 7.00 (1H, dd, J=8.5Hz; 2.0Hz, H-6⿲), 6.76 (1H, d, J=8.0Hz, H-5⿲), 6.26 (1H, d, J=16.0Hz, H-2). ¹³C NMR (DMSO-d₆): 51.2 (1-OCH₃), 167.0 (C-1), 113.7 (C-2), 145.2 (C-3), 125.5 (C-1⿲), 114.8 (C-2⿲), 145.6 (C-3⿲), 148.3 (C-4⿲), 115.7 (C-5⿲), 121.4 (C-6⿲).

Trilobolide-6-O-isobutyrate (8): white, amorphous solid. ¹H NMR (CDCl₃): 6.26 (1H, d, J=4.0Hz, H-13a), 5.98 (1H, dd, 3.0, 1.5Hz, H-7), 5.67 (1H, dd, J=3.0; 1.5Hz, H-6), 5.24 (1H, d, J=4.5Hz, H-9), 4.89 (1H, dd, J=8.0; 4.5Hz, H-8), 2.60 (1H, sept, J=7.0Hz, H-19), 2.01 (3H, s, H-23), 1.95 (3H, s, H-17), 1.36 (3H, s, H-15), 1.24 (3H, d, J=7.0Hz, H-20), 1.22 (3H, d, J=7.0Hz, H-21).¹³C NMR (CDCl₃): 73.2 (1), 24.2 (C-2), 41.8 (C-3), 71.3 (C-4), 45.1 (C-5), 68.2 (C-6), 43.7 (C-7), 72.2 (C-8), 70.8 (C-9), 41.5 (C-10), 134.3 (C-11), 169.5 (C-12), 119.3 (C-13), 26.6 (C-14), 14.5 (C-15), 170.7 (C-16), 21.2 (C-17), 176.4 (C-18), 34.6 (C-19), 18.6 (C-20), 19.2 (C-21), 169.3 (C-22), 20.4 (C-23).

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