Patients with obstructive sleep apnea (OSA) experience chronic intermittent hypoxia (CIH). OSA patients and CIH-treated rodents exhibit overactive sympathetic nervous system and hypertension, mediated through hyperactive carotid body (CB) chemoreflex. Activation of olfactory receptor 78 (Olfr78) by hydrogen sulfide (H2S) is implicated in CB activation and sympathetic nerve responses to CIH, but the downstream signaling pathways remain unknown. Given that odorant receptor signaling is coupled to adenylyl cyclase 3 (Adcy3), we hypothesized that Adcy3-dependent cyclic adenosine monophosphate (cAMP) contributes to CB and sympathetic responses to CIH. Our findings show that CIH increases cAMP levels in the CB, a response absent in Adcy3, Cth (encoding CSE), and Olfr78 null mice. CBs from Cth and Olfr78 mutant mice lacked a persulfidation response to CIH, indicating that Adcy3 activation requires Olfr78 activation by H2S in CIH. CIH also enhanced glomus cell Ca2+ influx, an effect absent in Cnga2 (encoding cyclic nucleotide-gated channel alpha2 subunit) and Adcy3 mutants, suggesting that CIH-induced cAMP mediates enhanced Ca2+ responses through cyclic nucleotide-gated channels. Furthermore, Adcy3 null mice did not exhibit either CB activation or sympathetic activation by CIH. These results demonstrate that Adcy3-dependent cAMP is a downstream signaling pathway to H2S/Olfr78, mediating CIH-induced CB activation, sympathetic activity and hypertension.

Patients with obstructive sleep apnea (OSA) experience chronic intermittent hypoxia (CIH). OSA patients and CIH-treated rodents exhibit autonomic dysfunction, characterized by overactive sympathetic nervous system and hypertension, mediated through hyperactive carotid body (CB) chemoreflex. Activation of olfactory receptor 78 (Olfr78) by hydrogen sulfide (H2S) is implicated in CB activation and autonomic responses to CIH, but the downstream signaling pathways remain unknown. Given that odorant receptor signaling is coupled to adenylyl cyclase 3 (Adcy3), we hypothesized that Adcy3-dependent cAMP contributes to CB and autonomic responses to CIH. Our findings show that CIH increases cAMP levels in the CB, a response absent in Adcy3, Cth, and Olfr78 null mice. CBs from Cth and Olfr78 mutant mice lacked persulfidation response to CIH, indicating that Adcy3 activation by CIH requires Olfr78 activation by H2S. CIH also enhanced glomus cell Ca2+ influx, an effect absent in Cnga2 and Adcy3 mutants, suggesting that CIH-induced cAMP mediates enhanced Ca2+ responses through cyclic nucleotide-gated channels. Furthermore, Adcy3 null mice did not exhibit neither CB activation nor autonomic dysfunction by CIH. These results demonstrate that Adcy3-dependent cAMP is a downstream signaling pathway to H2S/Olfr78, mediating CIH-induced CB activation and autonomic dysfunction. ### Competing Interest Statement The authors have declared no competing interest.

Obstructive sleep apnea (OSA), a widespread breathing disorder, leads to intermittent hypoxia (IH). Patients with OSA and IH-treated rodents exhibit heightened sympathetic nerve activity and hypertension. Previous studies reported transcriptional activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox) by HIF-1 (hypoxia-inducible factor-1) contribute to autonomic dysfunction in IH-treated rodents. Lysine acetylation, regulated by KATs (lysine acetyltransferases) and KDACs (lysine deacetylases), activates gene transcription and plays an important role in several physiological and pathological processes. This study tested the hypothesis that acetylation of HIF-1α by p300/CBP (CREB-binding protein) (KAT) activates Nox transcription, leading to sympathetic activation and hypertension. Experiments were performed on pheochromocytoma-12 cells and rats treated with IH. IH increased KAT activity, p300/CBP protein, HIF-1α lysine acetylation, HIF-1 transcription, and HIF-1 binding to the Nox4 gene promoter in pheochromocytoma-12 cells, and these responses were blocked by CTK7A, a selective p300/CBP inhibitor. Plasma norepinephrine (index of sympathetic activation) and blood pressures were elevated in IH-treated rats. These responses were associated with elevated p300/CBP protein, HIF-1α stabilization, transcriptional activation of Nox2 and Nox4 genes, and reactive oxygen species, and all these responses were absent in CTK7A-treated IH rats. These findings suggest lysine acetylation of HIF-1α by p300/CBP is an important contributor to sympathetic excitation and hypertension by IH.

Hypobaric hypoxia (HH) occurring at high altitudes activates the sympathetic nervous system (SNS) and increases circulating erythropoietin (EPO) levels. EPO stimulates red blood cell production (erythropoiesis), enhancing oxygen transport in arterial blood to counteract hypoxemia. The present study tested the hypothesis that SNS contributes to EPO activation by HH through epinephrine (EPI) release from the adrenal medullae. Adult male C57B6 mice were exposed to 18 h of HH (0.4 atm), and renal EPO mRNA and plasma EPO levels were measured. HH increased EPO mRNA and plasma EPO levels, and SNS activation, as indicated by elevated plasma norepinephrine (NE) and EPI levels. In adrenal-medullectomized mice, HH-induced EPO response was reduced, correlating with decreased circulating NE and absence of EPI elevation. EPI, but not NE infusion, mimicked the effects of HH in room air-breathing mice. EPO responses to HH were reduced with β-adrenergic receptor (AR) blockade using dl-propranolol and in β2 adrenergic receptor knockout mice. Mice with heterozygous Hif-2α deficiency (Hif-2α+/-), but not Hif-1α+/-, showed attenuated EPO gene activation and elevated plasma EPO levels in response to HH and EPI infusion. These results demonstrate that adrenal EPI facilitates the EPO gene activation by HH through the interaction of β2 AR with HIF-2α.NEW & NOTEWORTHY Hypobaric hypoxia activates the sympathetic nervous system (SNS) and the erythropoietin (EPO) gene. Whether SNS activation by hypoxia influences the EPO gene activation is an unresolved question. The present study demonstrates that adrenal epinephrine facilitates hypoxia-induced EPO gene activation through the interaction of β2 adrenergic receptors (β2 ARs) with the transcriptional activator HIF-2α.

Hypobaric hypoxia (HH) evokes a series of physiological adaptations, including carotid body (CB)–dependent ventilatory acclimatization to hypoxia (VAH), elevated blood pressure (BP), and stimulation of erythropoietin (Epo) gene in the kidney. Olfactory receptor 78 (Olfr78) is a G‐protein coupled receptor that has been implicated in CB response to acute hypoxia. Given that both CB and kidney express Olfr78, we tested the hypothesis that Olfr78 plays a role in the cardio‐respiratory and renal Epo gene responses to HH. Studies were performed on wild type (WT) and Olfr78 null mice reared in room air (control) or exposed to 18h of HH (0.4 atmospheres). HH treated WT exhibited: 1) VAH manifested as increased baseline breathing, and enhanced hypoxic ventilatory response (HVR; 12% O2); 2) elevated BP and plasma norepinephrine levels; and 3) increased baseline CB sensory nerve activity and augmented CB sensory nerve response to subsequent acute hypoxia‐ all these responses to HH are either markedly attenuated or absent in Olfr78 null mice. WT mice responded to HH with activation of the renal Epo gene expression and elevated plasma Epo levels, and these effects were attenuated or absent in Olfr78 null mice. The attenuated Epo activation by HH was accompanied with markedly reduced hypoxia‐inducible factor (HIF)‐2α protein and reduced activation of HIF‐2 target gene Sod‐1 in Olfr78 null mice, suggesting impaired transcriptional activation of HIF‐2 contributes to attenuated Epo responses to HH. These results suggest a role for Olfr78 in physiological adaptations to HH experienced at high altitude

Intermittent hypoxia (IH) is a hallmark manifestation of obstructive sleep apnea (OSA). Long term IH (LT-IH) triggers epigenetic reprogramming of the redox state involving DNA hypermethylation in the carotid body chemo reflex pathway resulting in persistent sympathetic activation and hypertension. Present study examined whether IH also activates epigenetic mechanism(s) other than DNA methylation. Histone modification by lysine acetylation is another major epigenetic mechanism associated with gene regulation. Equilibrium between the activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs) determine the level of lysine acetylation. Here we report that exposure of rat pheochromocytoma (PC)-12 cells to IH in vitro exhibited reduced HDAC enzyme activity due to proteasomal degradation of HDAC3 and HDAC5 proteins. Mechanistic investigations showed that IH-evoked decrease in HDAC activity increases lysine acetylation of α subunit of hypoxia inducible factor (HIF)-1α as well as Histone (H3) protein resulting in increased HIF-1 transcriptional activity. Trichostatin A (TSA), an inhibitor of HDACs, mimicked the effects of IH. Studies on rats treated with 10 days of IH or TSA showed reduced HDAC activity, HDAC5 protein, and increased HIF-1 dependent NADPH oxidase (NOX)-4 transcription in adrenal medullae (AM) resulting in elevated plasma catecholamines and blood pressure. Likewise, heme oxygenase (HO)-2 null mice, which exhibit IH because of high incidence of spontaneous apneas (apnea index 72 ± 1.2 apnea/h), also showed decreased HDAC activity and HDAC5 protein in the AM along with elevated circulating norepinephrine levels. These findings demonstrate that lysine acetylation of histone and non-histone proteins is an early epigenetic mechanism associated with sympathetic nerve activation and hypertension in rodent models of IH.

Olfactory receptor (Olfr) 78 participates in carotid body (CB) activation by acute hypoxia. We examined the role of Olfr78 in CB‐dependent sympathetic activation and hypertension in: 1) mice treated with chronic intermittent hypoxia (CIH) patterned after blood O2 profiles during obstructive sleep apnea (OSA) and 2) heme oxygenase‐2 (HO‐2) null mice, which exhibit OSA. CIH treated wild type (WT) mice showed: enhanced CB sensory nerve response to hypoxia and sensory long‐term facilitation (sLTF), hypertension, activation of the sympathetic nervous system as evidenced by spectral analysis of inter‐beat interval as well as elevated plasma nor‐epinephrine (NE) levels. All these responses were absent in Olfr78 null mice. HO‐2 null mice showed spontaneous apneas with an apnea index (AI) of 58±1.2 apneas/hour compared to AI of 8±0.8 apneas/hour in WT mice. CBs of HO‐2 null mice showed enhanced CB response to hypoxia and sLTF as well as elevated plasma NE levels and hypertension. The magnitude of hypertension correlated to AI in HO‐2 null mice (P<0.01). In striking contrast, HO‐2/Olfr78 double null mice showed stable breathing with an AI of 12±1.3 apneas/hour. HO‐2/Olfr78 double null mice showed absence of augmented CB response to hypoxia, sLTF, elevated plasma NE levels and hypertension. These results demonstrate that Olfr78 participates in CB activation and ensuing sympathetic nerve excitation and hypertension in two mouse models of OSA.

Hypobaric hypoxia (HH) experienced at high altitude initiates a series of physiological adaptations to maintain homeostasis. One such adaptation is the activation of the Epo gene which encodes the glycoprotein hormone erythropoietin (EPO). Increased circulating EPO levels defend against HH by facilitating blood O2 transport through increasing red blood cell production. HH also increases blood pressure (BP) through activation of the sympathetic nervous system and the ensuing elevation of circulating catecholamine levels. The present study examined the role of sympathetic nerve activation in HH-evoked Epo gene activation and elevated circulating levels of EPO. Studies were performed on adult, male wild-type (WT) mice treated with 18 hours of HH (0.4 atmospheres), simulating low O2 condition experienced at high altitude. Our results showed increased renal Epo gene abundance and elevated plasma EPO levels. Remarkably, these responses were either markedly attenuated or absent in mice with selective ablation of adrenal medulla as well as after treatment with propranolol, a non-selective beta-adrenergic receptor blocker. Moreover, infusion of epinephrine alone activated renal Epo gene and elevated plasma EPO levels. These results suggest that sympathetic nerve activation and the ensuing increase in plasma epinephrine contribute to Epo gene activation by HH.

Intermittent hypoxia (IH) is a hallmark manifestation of obstructive sleep apnea (OSA). Long term IH (LT‐IH) triggers epigenetic reprogramming of the redox state involving DNA hypermethylation leading to persistent sympathetic activation and hypertension. Present study examined whether IH also activates epigenetic mechanism(s) other than DNA methylation. Lysine modifications of histones is another major epigenetic mechanism associated with gene regulation. Interplay between lysine deacetylases (HDACs) and demethylases (KDMs) differentially regulate gene expression. Lysine acetylation of histone opens up the chromatin thereby facilitating binding of transcription factors. On the other hand, KDMs regulate transcription by demethylating histone lysines which activate gene expression. Here we report that exposure of rat pheochromocytoma (PC)‐12 cells to IH in vitro exhibit reduced HDAC5 and increased KDM6B enzyme activity leading to increased HIF‐1α stability and transcriptional activity. Treatment of rats with Trichostatin A (TSA), an inhibitor of HDACs increased HIF‐1 dependent NADPH oxidase (NOX)‐4 transcription, in adrenal medullae (AM), resulting in elevated plasma catecholamines and blood pressure. Treating IH exposed rats with GSKJ4 an inhibitor of KDMs blocked HIF‐1 dependent transcriptional activation of NOX4, as well as absence of elevated plasma catecholamines and hypertension. These findings indicate a hitherto uncharacterized role of HDACs and KDMs as early epigenetic regulators in IH‐augmented sympathetic nerve activation and hypertension in rodent models of IH.

Obstructive sleep apnea (OSA) is a common breathing disorder affecting a significant percentage of the adult population. OSA is an independent risk factor for cardiovascular disease (CVD); however, the underlying mechanisms are not completely understood. Since the severity of hypoxia correlates with some of the cardiovascular effects, intermittent hypoxia (IH) is thought to be one of the mechanisms by which OSA may cause CVD. Here, we investigated the effect of IH on endothelial cell (EC) activation, characterized by the expression of inflammatory genes, that is known to play an important role in the pathogenesis of CVD. Exposure of C57BL/6 mice to IH led to aortic EC activation, while in vitro exposure of ECs to IH failed to do so, suggesting that IH does not induce EC activation directly, but indirectly. One of the consequences of IH is activation of the sympathetic nervous system and catecholamine release. We found that exposure of mice to IH caused elevation of circulating levels of catecholamines. Inhibition of the IH-induced increase in catecholamines by pharmacologic inhibition or by adrenalectomy or carotid body ablation prevented the IH-induced EC activation in mice. Supporting a key role for catecholamines, epinephrine alone was sufficient to cause EC activation in vivo and in vitro. Together, these results suggested that IH does not directly induce EC activation, but does so indirectly via release of catecholamines. These results suggest that targeting IH-induced sympathetic nerve activity and catecholamine release may be a potential therapeutic target to attenuate the CV effects of OSA.

Catecholamine secretion from adrenal chromaffin cells is an important physiological mechanism for maintaining homeostasis during hypoxia. Here, we delineate carbon monoxide (CO)-sensitive hydrogen sulfide (H2S) signaling as an important mediator of hypoxia-induced catecholamine secretion from murine adrenal chromaffin cells. Heme oxygenase-2 derived CO is a physiological inhibitor of catcholamince secretion by hypoxia and the effects of CO involve inhibition of cystathionine γ-lyase-derived H2S production through soluble guanylyl cyclase-protein kinase G signaling cascade.

Chronic intermittent hypoxia (CIH) is a hallmark manifestation of obstructive sleep apnea (OSA), a widespread breathing disorder. CIH-treated rodents exhibit activation of the sympathetic nervous system and hypertension. Heightened carotid body (CB) activity has been implicated in CIH-induced hypertension. CB expresses high abundance of olfactory receptor (Olfr) 78, a G-protein coupled receptor. Olfr 78 null mice exhibit impaired CB sensory nerve response to acute hypoxia. Present study examined whether Olfr78 participates in CB-dependent activation of the sympathetic nervous system and hypertension in CIH-treated mice and in hemeoxygenase (HO)-2 null mice experiencing CIH as a consequence of naturally occurring OSA. CIH-treated wild-type (WT) mice showed hypertension, biomarkers of sympathetic nerve activation, and enhanced CB sensory nerve response to hypoxia and sensory long-term facilitation (sLTF), and these responses were absent in CIH-treated Olfr78 null mice. HO-2 null mice showed higher apnea index (AI) (58 +/- 1.2 apneas/h) than WT mice (AI = 8 +/- 0.8 apneas/h) and exhibited elevated blood pressure (BP), elevated plasma norepinephrine (NE) levels, and heightened CB sensory nerve response to hypoxia and sLTF. The magnitude of hypertension correlated with AI in HO-2 null mice. In contrast, HO-2/Olfr78 double null mice showed absence of elevated BP and plasma NE levels and augmented CB response to hypoxia and sLTF. These results demonstrate that Olfr78 participates in sympathetic nerve activation and hypertension and heightened CB activity in two murine models of CIH. NEW & NOTEWORTHY Carotid body (CB) sensory nerve activation is essential for sympathetic nerve excitation and hypertension in rodents treated with chronic intermittent hypoxia (CIH) simulating blood O2 profiles during obstructive sleep apnea (OSA). Here, we report that CIH-treated mice and hemeoxygenase (HO)-2-deficient mice, which show OSA phenotype, exhibit sympathetic excitation, hypertension, and CB activation. These effects are absent in Olfr78 null and Olfr78/HO-2 double null mice.

Emerging evidence suggests that gaseous molecules, carbon monoxide (CO) and hydrogen sulfide (H2S) generated by heme oxygenase-(HO)-2 and cystathionine γ-lyase (CSE), respectively, function as transmitters in the nervous system. Present study examined the roles of CO and H2S in hypoxia-induced catecholamine (CA) release from adrenal medullary chromaffin cells (AMC). Studies were performed on AMC from adult (≥6 weeks of age) wild type (WT), HO-2 null, CSE null and HO-2/CSE double null mice of either gender. CA secretion was determined by carbon fiber amperometry and [Ca2+]i by microflurometry using Fura-2. HO-2- and CSE immunoreactivities were seen in WT AMC, which were absent in HO-2 and CSE null mice. Hypoxia (medium pO2 30-38 mmHg) evoked CA release and elevated [Ca2+]i. The magnitude of hypoxic response was greater in HO-2 null mice and in HO inhibitor treated WT AMC compared to controls. H2S levels were elevated in HO-2 null AMC. Either pharmacological inhibition or genetic deletion of CSE prevented the augmented hypoxic responses of HO-2 null AMC and H2S donor rescued AMC responses to hypoxia in HO-2/CSE double null mice. CORM-3, a CO donor, prevented the augmented hypoxic responses in WT and HO-2 null AMC. CO donor reduced H2S levels in WT AMC. The effects of CO donor were blocked by either ODQ or 8pCT, inhibitors of soluble guanylyl cyclase (SGC) or protein kinase G, respectively. These results suggest that HO-2-derived CO inhibits hypoxia-evoked CA secretion from adult murine AMC involving soluble guanylyl cyclase (SGC)-protein kinase G (PKG)-dependent regulation of CSE- derived H2S.

Olfactory receptor (Olfr) 78 is expressed in the carotid bodies (CB) and participates in CB responses to acute hypoxia. Olfr78 is also expressed in the kidney, which is a major site of erythropoietin (Epo) production by hypoxia. The present study examined the role of Olfr78 in cardio-respiratory and renal Epo gene responses to hypobaric hypoxia (HH), simulating low O2 condition experienced at high altitude. Studies were performed on adult, male wild type (WT) and Olfr78 null mice treated with 18h of HH (0.4 atmospheres). HH treated WT mice exhibited increased baseline breathing, augmented hypoxic ventilatory response, elevated blood pressure and plasma norepinephrine (NE) levels. These effects were associated with increased baseline CB sensory nerve activity and augmented CB sensory nerve response to subsequent acute hypoxia. In contrast, HH treated Olfr78 null mice showed an absence of cardio-respiratory and CB sensory nerve responses, suggesting impaired CB-dependent cardiorespiratory adaptations. WT mice responded to HH with activation of the renal Epo gene expression and elevated plasma Epo levels, and these effects were attenuated or absent in Olfr78 null mice. The attenuated Epo activation by HH was accompanied with markedly reduced hypoxia-inducible factor (HIF)-2α protein and reduced activation of HIF-2 target gene Sod-1 in Olfr78 null mice, suggesting impaired transcriptional activation of HIF-2 contributes to attenuated Epo responses to HH. These results demonstrate a hitherto uncharacterized role for Olfr78 in cardio-respiratory adaptations and renal Epo gene activation by HH such as that experienced at high altitude.

As phytochemical-enriched edible greens, sweet potato (Ipomoea batatas L.) leaves have become popular. However, the profile and content of phytochemicals in sweet potato leaves are mostly unknown. We previously bred a purple-fleshed sweet potato P40 that demonstrated cancer prevention due to high levels of anthocyanins in the tuberous roots. The objectives of this study were to identify and quantify anthocyanins in P40 leaves when compared with the white-fleshed Bonita and orange-fleshed Beauregard. The mature leaves of P40 at 6-week vine stage were collected and extracted for anthocyanin analysis by HPLC-MS/MS. Fourteen anthocyanins, including a novel anthocyanin (peonidin 3-caffeoyl-p-coumaryl sophoroside-5-glucoside), were identified and quantitated. The contents of anthocyanins in P40 leaves (32.7 ± 2.9 mg/kg DW) were much lower than that in the root (13,100 ± 70 mg/kg DW). Furthermore, anthocyanin contents in P40 leaves were even lesser than those of the orange-fleshed Beauregard (334 ± 60.9 mg/kg DW) and white-fleshed Bonita (563 ± 50.4 mg/kg DW). Total phenolic contents as measured by Folin-Ciocalteu were 36.8 ± 4.8 mg GAE/g DW in the leaves of P40, but 41.2 ± 5.0 mg GAE/g DW in Beauregard and 46.7 ± 2.1 mg GAE/g DW in Bonita. No anthocyanin was detectable in the stem of these three sweet potato varieties. Taken together, this study reports for the first time the profile and content of anthocyanins in the leaves of three sweet potato varieties with a new anthocyanin identified. The unexpected lower levels of anthocyanins in the purple-fleshed sweet potato leaves when compared with either the counterpart tuberous roots or the control white-fleshed and orange-fleshed sweet potato varieties advanced our existing knowledge and also validated a diverse phenotype of anthocyanin biosynthesis between sweet potato leaves and roots.

Sorghum is a versatile grain generally consumed in Asia and Africa countries but is gaining interest in the United States due to its gluten-free and bioactive compound-enriched health benefits. There are many varieties of sorghum that come in a wide range of colors. Various phytochemical pigments that reside within different components of the sorghum kernel, especially in pericarp and endosperm, contribute to these genetic factor-dependent phenotypic colors. Various pericarp pigments are reflective of the certain phytochemical levels, which may include anthocyanins, carotenoids, and condensed tannins, etc. This chapter reviews recent studies on the association of the pericarp pigments in various sorghum accessions with anthocyanins and carotenoids, respectively. It covers aspects of the potential health benefits of these colored dietary constituents, however, further investigations are warranted to clarify the diversity of theses bioactive constituent interactions with genetic and environmental factors. How these phytochemicals correlate to the sorghum pericarp pigments could be important in future use of sorghum as a functional food for potential health benefits.

This review focused on the influence of environmental systems and/or factors including high tunnel, UV and visible light, fertilization, and irrigation on bioactive compounds in vegetables and fruits. Most studies reported that high tunnel reduced chicoric acid and luteolin in vegetables including lettuce and pac choi, and fruits including raspberry and tomato versus open field, although a few studies demonstrated that high tunnel did not significantly impact on the bioactive compounds. Light including UV such as photosynthetically active radiation (PAR), UV-A, and UV-B, and visible light especially red and blue light, significantly stimulated biosynthesis of anthocyanins, flavonoids, and phenolics, and promoted their contents in vegetables such as onion and spinach, and fruits for example blueberry and strawberry. The effect of fertilization including nitrogen, phosphorus, and potassium on bioactive phytochemicals (carotenoids, flavonoids, polyphenols) in vegetables (broccoli, kale) or fruits (tomato) varied among the cultivars. Water deficit usually increased anthocyanins, flavonoids, and phenolic acids in vegetables such as lettuce and red beet, and fruits including grape and pomegranate. Taken together, the bioactive compounds in vegetables and fruits in response to environmental factors were species- and varieties- dependent. The negative effect of environmental factors on bioactive compounds in vegetables and fruits can be overcome by selecting appropriate cultivars, while the positive effect can be further manipulated in horticultural production for potential consumer’s health benefits.

Phytochemical-enriched edible greens, sweet potato leaves (Ipomoea batatas L.), have become popular due to potential health benefits. However, the phytochemical contents in sweet potato leaves and their subsequent change over harvest stages and growth condition are mostly unknown. In this study, the anthocyanin profile and content in leaves of four sweet potato cultivars, i.e., white-skinned and white-fleshed Bonita, red-skinned and orange-fleshed Beauregard, red-skinned and white-fleshed Murasaki and purple-skinned and purple-fleshed P40, were evaluated. Fourteen anthocyanins were isolated and identified by HPLC-MSI/MS. The most abundant was cyanidin 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside, which comprised up to 20% of the total anthocyanins. Of the young leaves (1st and 2nd slip cuttings), Bonita contained the highest anthocyanin content followed by P40. Of the mature leaves (vine stage), Beauregard had the greatest anthocyanin (592.5 ± 86.4 mg/kg DW) and total phenolic (52.2 ± 3 mg GAE/g DW). It should be noted that the lowest anthocyanin and total phenolic content of shoots were found in P40, while tubers of P40 contain the highest content of each. Furthermore, the increase in leaf anthocyanin content over the growth stages that was observed in three of the cultivars but not in P40. No significant difference of anthocyanin content was found in Beauregard leaves grown in the high tunnels when compared with that in the open field. This study demonstrated for the first time that anthocyanin levels were significantly changed in response to various growth stages but not high tunnel condition, indicating that the effect of anthocyanin biosynthesis in sweet potato leaves is highly variable and genotype specific.

As phytochemical‐enriched edible greens, sweetpotato (Ipomoea batatas L.) leaves have become popular due to potential health benefits. However, the phytochemical contents in sweetpotato leaves and their subsequent change over harvest stages and growth condition are mostly unknown. In this study we determined the anthocyanin profile and content in leaves of four sweetpotato cultivars (Bonita, Beauregard, Murasaki, and P40). Fourteen anthocyanins, including one newly discovered, were identified by HPLC‐MS/MS. The most abundant was cyanidin 3‐caffeoyl‐p‐hydroxybenzoyl sophoroside‐5‐glucoside, which comprised up to 20% of the total anthocyanins. Of the young leaves (1st and 2nd slip cuttings), Bonita contained the highest anthocyanin content followed by P40. Of the mature leaves (vine stage), Beauregard had the greatest anthocyanin (391 mg/kg DW) and total phenolic (52 GAE/g DW) content. It should be noted that the lowest anthocyanin and total phenolic content of shoots were found in P40, while tubers of P40 contain the highest content of each. Furthermore, the increase in leaf anthocyanin content over the growth stages that was observed in three of the cultivars was absent in P40. No significant difference of anthocyanin content was found in Beauregard leaves grown in the high tunnels or open field.Support or Funding Informationsupported by USDA Cooperative KS511‐1001903