Naphthalene Derivatives and Quinones from Ventilago denticulata and Their Nitric Oxide Radical Scavenging,Antioxidant, Cytotoxic,Antibacterial, and Phosphodiesterase Inhibitory Activities

New naphthalene derivatives ( 1 and 2 ) and a new isomer ( 3 ) of ventilagolin, together with known anthraquinones, chrysophanol ( 4 ), physcion or emodin 3‐methyl ether ( 5 ), and emodin ( 6 ), were isolated from vines of Ventilago denticulata. The isolated compounds exhibited cytotoxic activity with IC₅₀ values of 1.15 – 40.54 μg/ml. Compounds 1 – 3 selectively exhibited weak antibacterial activity (MIC values of 200.0 – 400.0 μg/ml), while emodin ( 6 ) displayed moderate antibacterial activity with MIC value of 25.0 μg/ml. The isolated compounds showed nitric oxide and DPPH radical scavenging activities. Compounds 1 – 3 and 6 exhibited weak xanthine oxidase inhibitory activity, while emodin ( 6 ) acted as an aromatase inhibitor with the IC₅₀ value of 10.1 μm . Compounds 1 and 2 exhibited phosphodiesterase 5 inhibitory activity with IC₅₀ values of 8.28 μm and 6.48 μm , respectively.     

Bioactive Constituents of Juniperus turbinata Guss. from La Maddalena Archipelago

A comprehensive phytochemical study of Juniperus turbinata (Cupressaceae) collected from La Maddalena Archipelago (Sardinia, Italy) is reported. Both the essential oil and the ethanolic extract obtained from the aerial parts were analyzed. The essential oil appears to belong to a new chemotype compared to other Mediterranean juniper accessions, as it was favored by geographic isolation of the isles. It showed a low content of monoterpene hydrocarbons and α‐terpineol, ent‐manoyl oxide, 1,10‐di‐epi‐cubenol as the major constituents. The ethanolic fraction contained mainly diterpenoids. Among these, 15‐formyloxyimbricatolic acid ( 7 ) is a new natural product since it has hitherto been obtained only by synthetic route. The phenolic fraction contained biflavonoids: cupressuflavone ( 9 ), followed by minor amounts of amentoflavone ( 10 ) and hinokiflavone ( 11 ). The essential oil and six purified compounds ( 1 – 4 , 8 and 9 ) were assessed for biological activities, namely antioxidant (assessed by DPPH^·, ABTS^·+ and FRAP methods) and cytotoxic effects towards selected human tumor cell lines (MDA‐MB 231, A375 and HCT116 cells). Compound 3 exhibited higher radical scavenging activity against ABTS^·+ radical than the reference Trolox. Noteworthy, compound 8 showed powerful effects towards tumor cell lines, with IC₅₀ values in the range of 0.060 – 0.201 μm , which make it a promising anticancer drug candidate.     

Melanogenesis‐Inhibitory and Cytotoxic Activities of Diarylheptanoids from Acer nikoense Bark and Their Derivatives

Nine cyclic diarylheptanoids, 1 – 9 , including two new compounds, i.e., 9‐oxoacerogenin A ( 8 ) and 9‐O‐β‐D ‐glucopyranosylacerogenin K ( 9 ), along with three acyclic diarylheptanoids, 10 – 12 , and four phenolic compounds, 13 – 16 , were isolated from a MeOH extract of the bark of Acer nikoense (Aceraceae). Acid hydrolysis of 9 yielded acerogenin K ( 17 ) and D ‐glucose. Two of the cyclic diarylheptanoids, acerogenin A ( 1 ) and (R)‐acerogenin B ( 5 ), were converted to their ether and ester derivatives, 18 – 24 and 27 – 33 , respectively, and to the dehydrated derivatives, 25, 26, 34 , and 35 . Upon evaluation of compounds 1 – 16 and 18 – 35 for their inhibitory activities against melanogenesis in B16 melanoma cells, induced with α‐melanocyte‐stimulating hormone (α‐MSH), eight natural glycosides, i.e., six diarylheptanoid glycosides, 2 – 4, 6, 9 , and 12 , and two phenolic glycosides, 15 and 16 , exhibited inhibitory activities with 24–61% reduction of melanin content at 100 μM concentration with no or almost no toxicity to the cells (88–106% of cell viability at 100 μM ). In addition, when compounds 1 – 16 and 18 – 35 were evaluated for cytotoxic activity against human cancer cell lines, two natural acyclic diarylheptanoids, 10 and 11 , ten ether and ester derivatives, 18 – 22 and 27 – 31 , and two dehydrated derivatives, 34 and 35 , exhibited potent cytotoxicities against HL60 human leukemia cell line (IC₅₀ 8.1–19.3 μM ), and five compounds, 10, 11, 20, 29 , and 30 , against CRL1579 human melanoma cell line (IC₅₀ 10.1–18.4 μM ).     

Antioxidant,Anti-Skin-Aging,Anti-Inflammatory,and Anti-Acetylcholinesterase Activities of Rourea oligophlebia Extracts

The objective of this study was to evaluate the antioxidant, anti-skin-aging, anti-inflammatory, and anti-acetylcholinesterase activities of the hexane (n-hex), AcOEt, BuOH, MeOH, and aqueous extracts from R. oligophlebia roots. The total phenolic and flavonoid contents (TPC and TFC) were determined using Folin-Ciocalteu and AlCl₃ colorimetric assays. The antioxidant capacity was examined by reducing power (RP), ferric reducing antioxidant power (FRAP), ABTS⋅⁺, and DPPH⋅⁺ radical cation assays. All extracts potentially exhibited antioxidant activity with IC₅₀ values ranging from 2.93 to 5.73 μg/mL for ABTS⋅⁺ and from 5.69 to 7.65 μg/mL for DPPH⋅⁺ except the n-hex extract. The BuOH, MeOH, and aqueous extract possess promising anti-skin-aging activities, as observed by an attenuation of UV-A toxicity on human keratinocytes. We proposed that these anti-skin-aging properties are possibly due to direct scavenging activity against reactive oxygen species and upregulate cellular antioxidant machinery. Moreover, we found that the antioxidant capacity was well correlated with anti-inflammatory capacity against nitric oxide (NO) production in terms of the n-hex, AcOEt, and BuOH extracts with IC₅₀ values from 23.21 to 47.1 μg/mL. In contrast, these activities were found to be poorly correlated with AchE activity. To the best of our knowledge, this is the first report of the antioxidant, anti-skin-aging, anti-inflammatory, and anti-acetylcholinesterase activities of the extracts of R. oligophlebia roots. These findings indicated that this species could be a potential source of natural antioxidant, anti-aging, and anti-inflammatory agents. Consequently, it may be suggested as a medicinal plant that prevents diseases related to oxidative stress and inflammatory responses.     

Melanogenesis‐Inhibitory and Cytotoxic Activities of Chemical Constituents from the Leaves of Sauropus androgynus L. Merr. (Euphorbiaceae)

A new steroid, 20‐hydroxyisofucosterol (stigmasta‐5,24(28)‐diene‐3β,20β‐diol) ( 7 ), along with six known compounds 1 – 6 were isolated from the MeOH extract of the leaves of Sauropus androgynus L. Merr . (Euphorbiaceae). The structure of new steroid was determined by HR‐APCI‐MS and various NMR techniques in combination with literature data. Subsequently, their anti‐inflammatory, cytotoxic activities against five human cell lines, as well as inhibitory activities against the α‐MSH induced melanogenesis on the B16 cell line were evaluated. As the results, steroid compounds, 6 and 7 exhibited moderate cytotoxic to HL60, AZ521, SKBR3, and A549 tumor cell lines (IC₅₀ 26.9 – 45.1 μm ) with high tumor selectivity for A549 relative to WI38 cell lines (SI 2.6 and 3.0, resp.). And, flavonoid compounds, 4 and 5 exhibited superior inhibitory activities against melanogenesis (67.0 – 94.7% melanin content), even with no or low toxicity to the cells (90.1 – 99.6% cell viability) at the concentrations from 10 to 100 μm . Furthermore, Western blot analysis suggested that compound 5 could inhibit melanogenesis by suppressing the protein expressions of MITF, TRP‐1, TRP‐2, and tyrosinase.     

Polyphenol Characterization,Antioxidant and Skin Whitening Properties of Alnus cordata Stem Bark

In this study, we investigated the phenolic composition of the crude extract (MeOH 80 %) of Alnus cordata (Loisel .) Duby stem bark (ACE) and its antioxidant and skin whitening properties. RP‐LC‐DAD analysis showed a high content of hydroxycinnamic acids (47.64 %), flavanones (26.74 %) and diarylheptanoids (17.69 %). Furthermore, ACE exhibited a dose‐dependent antioxidant and free‐radical scavenging activity, expressed as half‐maximal inhibitory concentration (IC₅₀): Oxygen radical absorbance capacity (ORAC, IC₅₀ 1.78 μg mL^?1)>Trolox equivalent antioxidant capacity (TEAC, IC₅₀ 3.47 μg mL^?1)>2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH, IC₅₀ 5.83 μg mL^?1)>β‐carotene bleaching (IC₅₀ 11.58 μg mL^?1)>Ferric reducing antioxidant power (FRAP, IC₅₀ 17.28 μg mL^?1). Moreover, ACE was able to inhibit in vitro tyrosinase activity (IC₅₀ 77.44 μg mL^?1), l ‐DOPA auto‐oxidation (IC₅₀ 39.58 μg mL^?1) and in an in vivo model it exhibited bleaching effects on the pigmentation of zebrafish embryos (72 h post fertilization) without affecting their development and survival. In conclusion, results show that A. cordata stem bark may be considered a potential source of agents for the treatment of skin disorders due to its bleaching properties and favorable safety profiles, associated to a good antioxidant power.     

Variation in Essential Oil and Bioactive Compounds of Curcuma kwangsiensis Collected from Natural Habitats

The chemical compositions of essential oils (EOs) extracted from Curcuma kwangsiensis rhizomes collected from six natural habitats in P. R. China were evaluated using gas chromatography/mass spectrometry (GC/MS). Fifty‐seven components were identified from the six EOs, and their main constituents were 8,9‐dehydro‐9‐formyl‐cycloisolongifolene (2.37 – 42.59%), germacrone (6.53 – 22.20%), and l ‐camphor (0.19 – 6.12%). The six EOs exhibited different DPPH radical‐scavenging activities (IC₅₀, 2.24 – 31.03 μg/ml), with the activity of most of EOs being much higher than that of Trolox C (IC₅₀, 10.49 μg/ml) and BHT (IC₅₀, 54.13 μg/ml). Most EOs had potent antimicrobial effects against the tested bacteria and fungus. They also exhibited cytotoxicity against B16 (IC₅₀, 4.44 – 147.4 μg/ml) and LNCaP cells (IC₅₀, 73.94 – 429.25 μg/ml). The EOs showed excellent anti‐inflammatory action by significantly downregulating expression of pro‐inflammatory cytokines, cyclooxygenase‐2, and tumor necrosis factor‐α. This study provides insight into the interrelation among growth location, phytoconstituents, and bioactivities, and the results indicate the potential of C. kwangsiensis as natural nutrients, medicines, and others additives.     

Phenolic Compounds and Antioxidant Activity of Different Organs of Potentilla fruticosa L. from Two Main Production Areas of China

This report compared the phenolic compounds and antioxidant activity of the leaves, flowers, and stems of Potentilla fruticosa L. collected from two main production areas of P. R. China (Taibai Mountains and the Qinghai Huzhu Northern Mountains). The results indicated that there were significant differences in the phenol contents and antioxidant activities among the different organs and between the two productions. High‐performance liquid‐chromatography analysis indicated that hyperoside, (+)‐catechin, ellagic acid, and rutin were the primary compounds in leaves and flowers; for stems, the content of six phenolic compounds, from two productions, were the lowest. The 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH), 2,2‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) di‐ammonium salt (ABTS), ferric reducing power (FRAP), lipid peroxidation assays, and microbial test system (MTS) were used to evaluate the antioxidant activity. The results demonstrated that the leaves from two productions exhibited powerful antioxidant activity than other organs, which did not significantly differ from that of the positive control (rutin), followed by the flowers and stems. The correlation between the content of phytochemicals and the antioxidant activities of different organs showed that the total phenol, tannin, hyperoside, and (+)‐catechin contents may influence the antioxidant activity, and these compounds can be used as markers for the quality control of P. fruticosa.     

Melanogenesis‐Inhibitory and Cytotoxic Activities of Limonoids,Alkaloids, and Phenolic Compounds from Phellodendron amurense Bark

Four limonoids, 1  –  4 , five alkaloids, 5  –  9 , and four phenolic compounds, 10  –  13 , were isolated from a MeOH extract of the bark of Phellodendron amurense (Rutaceae). Among these, compound 13 was new, and its structure was established as rel‐(1R,2R,3R)‐5‐hydroxy‐3‐(4‐hydroxy‐3‐methoxyphenyl)‐6‐methoxy‐1‐(methoxycarbonylmethyl)indane‐2‐carboxylic acid methyl ester (γ‐di(methyl ferulate)) based on the spectrometric analysis. Upon evaluation of compounds 1  –  13 against the melanogenesis in the B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), four compounds, limonin ( 1 ), noroxyhydrastinine ( 6 ), haplopine ( 7 ), and 4‐methoxy‐1‐methylquinolin‐2(1H)‐one ( 8 ), exhibited potent melanogenesis‐inhibitory activities with almost no toxicity to the cells. Western blot analysis revealed that compound 6 inhibited melanogenesis, at least in part, by inhibiting the expression of protein levels of tyrosinase, TRP‐1, and TRP‐2 in α‐MSH‐stimulated B16 melanoma cells. In addition, when compounds 1  –  13 were evaluated for their cytotoxic activities against leukemia (HL60), lung (A549), duodenum (AZ521), and breast (SK‐BR‐3) cancer cell lines, five compounds, berberine ( 5 ), 8 , canthin‐6‐one ( 9 ), α‐di‐(methyl ferulate) ( 12 ), and 13 , exhibited cytotoxicities against one or more cancer cell lines with IC₅₀ values in the range of 2.6 – 90.0 μm . In particular, compound 5 exhibited strong cytotoxicity against AZ521 (IC₅₀ 2.6 μm ) which was superior to that of the reference cisplatin (IC₅₀ 9.5 μm ).     

Sesquiterpene Lactones with COX‐2 Inhibition Activity from Artemisia lavandulaefolia

Two new sesquiterpene lactones, artelavanolides A ( 1 ) and B ( 2 ), and four known sesquiterpene lactones ( 3 – 6 ) were isolated from the leaves of Artemisia lavandulaefolia. Their structures were elucidated based on the analysis of spectroscopic data (1D, 2D‐NMR and HR‐ESI‐MS). The absolute configuration of 1 was determined by the analysis of single‐crystal X‐ray diffraction data. Artelavanolide A ( 1 ) is a rare sesquiterpene lactone possessing an unusual skeleton with the linkage of Me(14)–C(1) that is probably formed through a rearrangement of the guaiane‐type sesquiterpenoids. Artelavanolide B ( 2 ) is a new highly unsaturated guaianolide. Compounds 1 – 6 were tested for activities on the inhibition of COX‐2 enzyme in vitro. All of compounds exhibited inhibitory activity against COX‐2 with IC₅₀ values ranging from 43.29 to 287.07 μm compared with the positive control, celecoxib (IC₅₀ = 18.10 μm ). Among them, 3 showed the best COX‐2 inhibitory activity with an IC₅₀ value of 43.29 μm .     

Antiviral Triketone‐Phloroglucinol‐Monoterpene Adducts from Callistemon rigidus

Callistrilones F – K ( 1 – 6 ), six new triketone‐phloroglucinol‐monoterpene hybrids were isolated from the twigs and leaves of Callistemon rigidus. Their structures with absolute configurations were established by a combination analysis of NMR spectra, X‐ray diffraction, and electronic circular dichroism (ECD) calculations. Compounds 3 and 4 exhibited moderate inhibitory activities against herpes simplex virus (HSV‐1) with IC₅₀ values of 10.00 ± 2.50 and 12.50 ± 1.30 μm , respectively.     

GC-MS analysis and in vitro antioxidant and enzyme inhibitory activities of essential oil from aerial parts of endemic Thymus spathulifolius Hausskn. et Velen

We investigated the antioxidant and enzyme inhibitory activities and chemical composition of the hydro-distilled essential oil (0.35% yield) from aerial parts of Thymus spathulifolius. Antioxidant capacity of the oil was assessed by different methods including free radical scavenging (DPPH and ABTS), reducing power (FRAP and CUPRAC) and phosphomolybdenum assay. Inhibitory activities were analyzed against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-amylase, α-glucosidase, and tyrosinase. Twenty-one constituents were identified representing 97.2% of the total oil with thymol (50.5%), borneol (16.7%) and carvacrol (7.7%) as the major components. The essential oil exhibited good antioxidant activity with IC₅₀ values of 3.82 and 0.22?mg/mL determined by free radical scavenging DPPH and ABTS, respectively. EC₅₀ values of FRAP and CUPRAC were found to be 0.12 and 0.34?mg/mL, respectively. The results of the present study support the uses of T. spathulifolius essential oil as a source of natural antioxidants and bioactivities for functional foods and phytomedicines.     

Chemical Composition,Antibacterial, Antioxidant and in Vitro Antidiabetic Activities of Essential Oils from Eruca vesicaria

This work describes the study of the chemical composition and bioactivity of the essential oils (EOs) of the different organs (leaves, flowers, stems and roots) from Eruca vesicaria. According to the GC and GC/MS analysis, all the EOs were dominated by erucin (4‐methylthiobutyl isothiocyanate) with a percentage ranging from 17.9 % (leaves) to 98.5 % (roots). The isolated EOs were evaluated for their antioxidant (DPPH, ABTS and β‐carotene/linoleic acid), antibacterial and inhibitory property against α‐amylase and α‐glucosidase. Most EOs exhibited an interesting α‐glucosidase and α‐amylase inhibitory potential. The roots essential oil was found to be the most active with IC₅₀ values of 0.80±0.06 and 0.11±0.01 μg mL^?1, respectively. The essential oil of roots exhibited the highest antioxidant activity (DPPH, PI=92.76±0.01 %; ABTS, PI=78.87±0.19; and β‐carotene, PI=56.1±0.01 %). The isolated oils were also tested for their antibacterial activity against two Gram‐positive and three Gram‐negative bacteria. Moderate results have been noted by comparison with Gentamicin used as positive control.     

Comparison of Phytochemical Composition and Biological Activities of Rubus ulmifolius Extracts Originating from Four Regions of Tunisia

In the current study, the phenolic composition, antioxidant and antimicrobial activities of extracts from Rubus ulmifolius Schott leaves harvested in four localities (Sejnen, Tabarka, Faija and Ain drahem) in Tunisia were investigated for the first time. Great differences were found for the chemical composition, total phenol contents and biological activities among the evaluated extracts. HPLC analysis of methanolic extracts showed that the dominant compounds were kaempferol 3‐O‐rutinoside and naringenine. In addition, significant correlations were observed between antioxidant activities and phenolic contents. In fact, leaves collected from Sejnen presented higher total phenol content (53.32 mg GAE/g DW) and antioxidant activities (IC₅₀ = 39.40 mg/l) than the others samples. All extracts showed significant antimicrobial activity against six used bacteria with the inhibition zones diameters and minimal inhibitory concentration values were in the range of 8 – 16 mm and 6.25 – 25 mg/ml, respectively. The highest antimicrobial activities were recorded in Sejnen extract against Gram‐positive bacteria.     

Chemical Composition and Antioxidant,Antiparasitic, Cytotoxicity and Antimicrobial Potential of the Algerian Limonium Oleifolium Mill. Essential Oil and Organic Extracts

This work aimed to investigate, for the first time, the chemical composition, antioxidant, antiparasitic, cytotoxicity, and antimicrobial activities of the aromatic plant Limonium oleifolium Mill. essential oil (EO) and organic extracts. L. oleifolium aerial parts essential oil was analyzed by GC-FID and GC-MS, and 46 constituents representing 98.25±1.12 % of the oil were identified. γ-Muurolene (10.81±0.07 %), cis-caryophyllene (7.71±0.06 %), o-cymene (7.07±0.01 %) and α-copaene (5.02±0.05 %) were the essential oil main compounds. The antioxidant activity of L. oleifolium EO and organic extracts (MeOH, CHCl₃, AcOEt, BuOH) was explored using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ABTS, β-carotene/linoleic acid, cupric reducing antioxidant capacity (CUPRAC), and ferric reducing power assays. The results showed that L. oleifolium EO exhibit antioxidant capacity (IC₅₀=17.40±1.32 μg/mL for DPPH assay, IC₅₀=29.82±1.08 μg/mL for β-carotene assay, IC₅₀=25.23±1.01 μg/mL for ABTS assay, IC₅₀=9.11±0.08 μg/mL for CUPRAC assay and IC₅₀=19.41±2.06 mg/mL for reducing power assay). Additionally, the EO showed significant activity against trophozoite form of Acanthamoeba castellanii (IC₅₀=7.48±0.41 μg/mL) and promastigote form of Leishmania amazonensis (IC₅₀=19.36±1.06 μg/mL) and low cytotoxicity on murine macrophages (LC₅₀ 90.23±1.09 μg/mL), as well as good antimicrobial activity against Staphylococcus aureus, Escherichia coli, Klebsiella oxytoca, and Pseudomonas aeruginosa. These results suggest that L. oleifolium essential oil is a valuable source of bioactive compounds presenting antioxidant, antiparasitic, and antimicrobial activities. Furthermore, it is considered nontoxic.     

Chemical Composition and Biological Activities of the Essential Oil of Athanasia brownii Hochr. (Asteraceae) Endemic to Madagascar

The essential oil obtained from hydrodistillation of flowering aerial parts of Athanasia brownii (Asteraceae) was studied for its chemical composition by GC/FID and GC/MS, and for biological activity, namely, antioxidant, antimicrobial, and chemopreventive potential, by DPPH (=2,2‐diphenyl‐1‐picrylhydrazyl), ABTS (=2,2′‐azinobis[3‐ethylbenzothioline‐6‐sulfonic acid), and FRAP (=ferric reducing antioxidant power), disk diffusion test, and MTT (=3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, respectively. The oil was characterized by a high content of oxygenated sesquiterpenes (71.2%), with selin‐11‐en‐4α‐ol (24.6%), caryophyllene oxide (8.7%), humulene epoxide II (5.1%), and (E)‐nerolidol (4.9%) as the predominant compounds. The oil showed a moderate activity against streptococci as well as radical‐scavenging potential, while the inhibitory effects against human cancer cells examined such as A375 (malignant melanoma) and HCT 116 (colon carcinoma) were significant, with IC₅₀ values of 19.85 and 29.53 μg/ml, respectively.     

Biological Activities of Triterpenoids and Phenolic Compounds from Myrica cerifera Bark

Seven triterpenoids, 1  –  7 , two diarylheptanoids, 8 and 9 , four phenolic compounds, 10  –  13 , and three other compounds, 14  –  16 , were isolated from the hexane and MeOH extracts of the bark of Myrica cerifera L. (Myricaceae). Among these compounds, betulin ( 1 ), ursolic acid ( 3 ), and myricanol ( 8 ) exhibited cytotoxic activities against HL60 (leukemia), A549 (lung), and SK‐BR‐3 (breast) human cancer cell lines (IC₅₀ 3.1 – 24.2 μm ). Compound 8 induced apoptotic cell death in HL60 cells (IC₅₀ 5.3 μm ) upon evaluation of the apoptosis‐inducing activity by flow cytometric analysis and by Hoechst 33342 staining method. Western blot analysis on HL60 cells revealed that 8 activated caspases‐3, ‐8, and ‐9 suggesting that 8 induced apoptosis via both mitochondrial and death receptor pathways in HL60. Upon evaluation of the melanogenesis‐inhibitory activity in B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), erythrodiol ( 7 ), 4‐hydroxy‐2‐methoxyphenyl β‐d ‐glucopyranoside ( 13 ), and butyl quinate ( 15 ) exhibited inhibitory effects (65.4 – 86.0% melanin content) with no, or almost no, toxicity to the cells (85.9 – 107.4% cell viability) at 100 μm concentration. In addition, 8 , myricanone ( 9 ), myricitrin ( 10 ), protocatechuic acid ( 11 ), and gallic acid ( 12 ) revealed potent DPPH radical‐scavenging activities (IC₅₀ 6.9 – 20.5 μm ).